Evidence Collection
Expert-defined terms from the Crime Scene Investigation course at LearnUNI. Free to read, free to share, paired with a professional course.
Accession Number #
Accession Number
Concept #
Unique identifier assigned to each piece of evidence when it enters the laboratory.
Explanation #
The accession number links the physical item to all documentation, ensuring traceability throughout analysis.
Example #
A blood‑stained swab receives accession number 2023‑00123.
Practical application #
Facilitates database searches and retrieval for future review.
Challenges #
Mis‑recording or duplication can break the evidentiary link and jeopardize admissibility.
Admissibility #
Admissibility
Concept #
Legal standard determining whether evidence may be presented in court.
Explanation #
Evidence must be relevant, reliable, and obtained lawfully to be admissible.
Example #
A fingerprint lifted with proper technique is admissible, whereas a contaminated sample may be excluded.
Practical application #
Guides investigators in collection methods to meet judicial requirements.
Challenges #
Defense challenges may argue constitutional violations or chain‑of‑custody gaps.
Alcohol Swab #
Alcohol Swab
Concept #
Small cotton swab pre‑moistened with isopropyl alcohol used for surface cleaning.
Explanation #
Used to sterilize a surface before collecting trace evidence, preventing cross‑contamination.
Example #
An officer swabs the handle of a pistol before gathering latent prints.
Practical application #
Ensures that only target material is collected from a suspect area.
Challenges #
Over‑wetting can degrade DNA, while insufficient cleaning may leave residual contaminants.
Archival Storage #
Archival Storage
Concept #
Long‑term preservation method for evidence that may be needed in future proceedings.
Explanation #
Evidence is stored under controlled temperature, humidity, and lighting to prevent degradation.
Example #
Fire‑arm cartridges are kept in a low‑humidity cabinet for up to ten years.
Practical application #
Allows re‑examination with new technologies such as advanced DNA profiling.
Challenges #
Space limitations and resource costs can restrict optimal storage conditions.
Audio Surveillance #
Audio Surveillance
Concept #
Recording of ambient sound at a crime scene for investigative or evidentiary purposes.
Explanation #
Captures verbal statements, background noises, and acoustic signatures that may corroborate other evidence.
Example #
A hidden microphone records a suspect’s confession in a suspect’s vehicle.
Practical application #
Provides corroborative evidence when visual cues are limited.
Challenges #
Legal restrictions on consent, background noise interference, and equipment reliability.
Ballistics Examination #
Ballistics Examination
Concept #
Scientific analysis of firearms, ammunition, and related markings.
Explanation #
Determines the source of a projectile by comparing striations and impressions on bullets and casings.
Example #
Matching a recovered 9mm bullet to a suspect’s handgun.
Practical application #
Links a weapon to a crime, supporting prosecution.
Challenges #
Surface damage, incomplete recovery, and limited comparison databases can impede accurate matches.
Biological Sample #
Biological Sample
Concept #
Any tissue, fluid, or cellular material that may contain DNA or other biological markers.
Explanation #
Collected for genetic profiling, toxicology, or serological testing.
Example #
Saliva on a cigarette butt is a biological sample.
Practical application #
Establishes identity or presence of individuals at a scene.
Challenges #
Degradation due to heat, moisture, or time can reduce analytical value.
Chain of Custody #
Chain of Custody
Concept #
Documented chronological record of evidence handling from collection to presentation.
Explanation #
Every transfer, storage, and analysis step is recorded to maintain integrity.
Example #
A signed chain‑of‑custody form notes each officer who handled a murder weapon.
Practical application #
Provides courts confidence that evidence has not been altered.
Challenges #
Gaps or inconsistencies can lead to evidence suppression.
Cold Case Review #
Cold Case Review
Concept #
Re‑examination of unsolved crimes using new techniques or information.
Explanation #
Revisits evidence with advanced technologies such as next‑generation DNA sequencing.
Example #
Re‑testing hair from a 1998 homicide leads to a DNA match.
Practical application #
Offers closure to victims’ families and potential convictions.
Challenges #
Deteriorated evidence and limited resources may hinder progress.
Contamination Control #
Contamination Control
Concept #
Procedures designed to prevent introduction of foreign material into evidence.
Explanation #
Involves using gloves, masks, and clean tools, and maintaining separate work areas.
Example #
Wearing nitrile gloves while collecting a bloodstain to avoid DNA transfer.
Practical application #
Preserves the purity of the sample for accurate analysis.
Challenges #
Human error and inadequate training can compromise control measures.
Coroner’s Report #
Coroner’s Report
Concept #
Official document summarizing findings from a post‑mortem examination.
Explanation #
Details cause and manner of death, toxicology results, and any injuries observed.
Example #
The report indicates death by blunt force trauma with alcohol intoxication.
Practical application #
Provides crucial information for criminal investigations and court testimony.
Challenges #
Variability in report detail and potential bias can affect investigative direction.
Crime Scene Tape #
Crime Scene Tape
Concept #
Physical barrier used to secure a crime scene from unauthorized entry.
Explanation #
Typically bright orange or red, the tape demarcates the restricted area.
Example #
Yellow police tape encircles a burglary site to preserve evidence.
Practical application #
Prevents contamination and maintains scene integrity.
Challenges #
Improper placement can obscure evidence or impede first responders.
Cross‑Contamination #
Cross‑Contamination
Concept #
Transfer of material from one sample to another, potentially creating false associations.
Explanation #
Occurs when tools or personnel inadvertently introduce foreign DNA or substances.
Example #
Using the same swab on two different surfaces without changing gloves.
Practical application #
Highlighted in training to reinforce strict protocols.
Challenges #
Difficult to detect after the fact, leading to wrongful convictions or acquittals.
DNA Profiling #
DNA Profiling
Concept #
Laboratory technique that generates a genetic fingerprint unique to an individual.
Explanation #
Amplifies specific DNA regions to compare with known samples.
Example #
Matching a suspect’s DNA to a semen stain recovered from a victim.
Practical application #
Provides strong evidentiary support for identification.
Challenges #
Low‑quantity or degraded samples may produce partial profiles, requiring careful interpretation.
Digital Evidence #
Digital Evidence
Concept #
Information stored or transmitted in electronic form that may be used in legal proceedings.
Explanation #
Includes files, logs, emails, and images retrieved from devices.
Example #
Extracting a deleted text message from a suspect’s smartphone.
Practical application #
Can establish timelines, motives, or alibis.
Challenges #
Rapid technology changes, encryption, and jurisdictional issues complicate collection.
Disposal Protocol #
Disposal Protocol
Concept #
Procedure for safely discarding evidence that is no longer needed.
Explanation #
Involves documentation, secure transport, and compliance with legal standards.
Example #
Shredding counterfeit money seized during an operation.
Practical application #
Prevents misuse of discarded items and maintains confidentiality.
Challenges #
Ensuring complete destruction and proper documentation to avoid accusations of tampering.
Document Examination #
Document Examination
Concept #
Analytical process that assesses the authenticity and origin of written or printed material.
Explanation #
Evaluates ink, paper, typeface, and alterations.
Example #
Determining that a forged signature was created using a ballpoint pen.
Practical application #
Supports fraud investigations and validates contracts.
Challenges #
Subtle variations and skilled forgeries demand high expertise.
Evidence Bag #
Evidence Bag
Concept #
Sealed container used to transport collected items while protecting them from contamination.
Explanation #
Often made of nylon or paper with a zip lock and evidence tag attached.
Example #
Placing a torn piece of clothing into a paper evidence bag.
Practical application #
Maintains sample integrity during movement between locations.
Challenges #
Inappropriate bag material may cause moisture buildup or static damage.
Evidence Log #
Evidence Log
Concept #
Chronological record of all evidence received, processed, and released.
Explanation #
Includes details such as description, location, and responsible personnel.
Example #
An entry notes that evidence #2023‑00123 was transferred to the forensic lab on June 1.
Practical application #
Enables auditors to verify handling procedures.
Challenges #
Incomplete entries or illegible handwriting can undermine credibility.
Evidence Preservation #
Evidence Preservation
Concept #
Methods employed to maintain the condition of collected items until analysis.
Explanation #
Includes temperature regulation, protective packaging, and avoidance of light exposure.
Example #
Storing blood samples at 4°C to prevent bacterial growth.
Practical application #
Ensures that later testing yields reliable results.
Challenges #
Resource constraints may limit optimal preservation environments.
Fiber Analysis #
Fiber Analysis
Concept #
Microscopic examination of textile fibers to link a suspect or object to a crime scene.
Explanation #
Determines fiber type, color, weave, and any unique characteristics.
Example #
Matching a carpet fiber found on a victim’s clothing to a specific carpet manufacturer.
Practical application #
Provides associative evidence when other links are weak.
Challenges #
High prevalence of common fibers can reduce discriminative power.
Forensic Anthropology #
Forensic Anthropology
Concept #
Scientific study of human skeletal remains to assist in identification and cause of death.
Explanation #
Determines age, sex, ancestry, and trauma patterns from bones.
Example #
Identifying a skull as belonging to a male aged 30‑35 years.
Practical application #
Helps locate missing persons and supports homicide investigations.
Challenges #
Fragmented remains and post‑mortem damage can limit conclusions.
Forensic Entomology #
Forensic Entomology
Concept #
Use of insects and their developmental stages to estimate post‑mortem intervals.
Explanation #
Analyzes species present on a corpse and calculates time since death.
Example #
Determining that a body has been deceased for 48 hours based on maggot growth.
Practical application #
Provides time‑frame evidence when other data are unavailable.
Challenges #
Environmental variables such as temperature and humidity affect insect development rates.
Fingerprint Lift #
Fingerprint Lift
Concept #
Technique for transferring latent prints from a surface onto a backing material for analysis.
Explanation #
Uses adhesive tape or gel lifters to capture the print without distortion.
Example #
Applying a clear adhesive tape to a glass door to retrieve a fingerprint.
Practical application #
Preserves prints for comparison against known databases.
Challenges #
Porous surfaces may yield incomplete lifts, and moisture can cause smearing.
Forensic Light Source (FLS) #
Forensic Light Source (FLS)
Concept #
Specialized illumination equipment used to reveal hidden evidence.
Explanation #
Emits specific wavelengths (e.g., UV, infrared) to enhance stains, fibers, or bodily fluids.
Example #
Using a 415 nm blue light to visualize bloodstains invisible to the naked eye.
Practical application #
Increases detection rates of trace evidence.
Challenges #
Incorrect wavelength selection can produce false positives or miss evidence.
Garbage Can Test #
Garbage Can Test
Concept #
Rapid field method for assessing whether a surface may contain biological material.
Explanation #
Applies a reagent that changes color in the presence of blood, saliva, or semen.
Example #
A pink color appears after applying the Kastle‑Meyer test to a stain.
Practical application #
Allows investigators to prioritize samples for laboratory analysis.
Challenges #
Cross‑reactivity with non‑target substances can lead to false positives.
Heat‑Sensitive Dye #
Heat‑Sensitive Dye
Concept #
Chemical indicator that changes color when exposed to elevated temperatures.
Explanation #
Placed on evidence containers to detect improper storage conditions.
Example #
A dye turns orange if a blood sample is stored above 30 °C for prolonged periods.
Practical application #
Alerts technicians to potential degradation before analysis.
Challenges #
Dyes may be affected by ambient light or humidity, requiring careful calibration.
Human Remains Identification (HRI) #
Human Remains Identification (HRI)
Concept #
Process of establishing the identity of deceased individuals using forensic methods.
Explanation #
Combines multiple data sources such as DNA, fingerprints, and osteological features.
Example #
Matching a victim’s dental X‑ray to a missing person’s record.
Practical application #
Provides closure for families and legal closure for investigations.
Challenges #
Fragmented remains and lack of ante‑mortem records can impede identification.
Impression Evidence #
Impression Evidence
Concept #
Physical marks left on a surface by an object, such as shoeprints or tire tracks.
Explanation #
Captured by casting, photography, or digital scanning for comparison.
Example #
Casting a shoeprint in a mud‑filled alleyway using dental stone.
Practical application #
Links a suspect’s footwear to a crime scene.
Challenges #
Distortion from environmental factors and incomplete impressions reduce reliability.
Immunochromatographic Test #
Immunochromatographic Test
Concept #
Rapid, point‑of‑care assay that detects specific antigens using antibodies.
Explanation #
A sample migrates along a membrane; a visible line indicates presence of the target.
Example #
A rapid test indicating the presence of human hemoglobin in a stain.
Practical application #
Provides quick screening results on scene.
Challenges #
Sensitivity may be lower than laboratory methods, leading to false negatives.
Incineration #
Incineration
Concept #
Controlled burning of evidence that cannot be retained or poses biohazard risks.
Explanation #
Conducted in a secure furnace with temperature monitoring to ensure complete combustion.
Example #
Incinerating a batch of counterfeit documents after the case concludes.
Practical application #
Guarantees irreversible destruction of sensitive material.
Challenges #
Requires documentation to prove compliance and prevent allegations of evidence tampering.
Instrumental Analysis #
Instrumental Analysis
Concept #
Use of scientific instruments to examine evidence at a molecular level.
Explanation #
Techniques such as GC‑MS or FTIR identify chemical compositions.
Example #
Analyzing paint chips with Fourier‑transform infrared spectroscopy to determine polymer type.
Practical application #
Provides definitive identification of unknown substances.
Challenges #
Requires specialized equipment, trained analysts, and may be time‑consuming.
Judicial Notice #
Judicial Notice
Concept #
Court’s acceptance of a fact as true without requiring formal proof.
Explanation #
Applies when information is widely known or easily verifiable.
Example #
A court taking judicial notice that a certain chemical has a known boiling point.
Practical application #
Streamlines proceedings by avoiding unnecessary expert testimony.
Challenges #
Misapplication can lead to acceptance of inaccurate or disputed facts.
K‑Fit Test #
K‑Fit Test
Concept #
Statistical method used to assess the likelihood that a DNA profile matches a suspect.
Explanation #
Calculates the probability that a profile would occur in the general population.
Example #
A K‑Fit value of 1 in 10 million supports a strong match.
Practical application #
Assists jurors in understanding DNA evidence weight.
Challenges #
Requires accurate population databases and may be misinterpreted by lay audiences.
Latent Print Development #
Latent Print Development
Concept #
Process of visualizing invisible fingerprints on various substrates.
Explanation #
Uses chemicals or physical methods to make prints visible for collection.
Example #
Applying cyanoacrylate fumes to a plastic bag to reveal a latent print.
Practical application #
Enables capture of prints that would otherwise remain hidden.
Challenges #
Certain surfaces (e.g., oily or wet) may resist development, and some chemicals can damage evidence.
Legal Hold #
Legal Hold
Concept #
Directive to preserve all potentially relevant evidence for litigation.
Explanation #
Requires organizations to suspend routine disposal of electronic or physical records.
Example #
A police department issuing a legal hold on all body‑camera footage related to an ongoing homicide case.
Practical application #
Prevents spoliation and ensures compliance with discovery obligations.
Challenges #
Coordination across departments and maintaining chain of custody over extended periods.
Logistics Chain #
Logistics Chain
Concept #
Coordination of resources, transport, and personnel involved in evidence handling.
Explanation #
Ensures timely, secure movement of items from collection to laboratory.
Example #
Scheduling a sealed courier service to deliver narcotics evidence to a federal lab.
Practical application #
Reduces delays and risks of loss or damage.
Challenges #
Geographic distance, limited secure vehicles, and scheduling conflicts can cause bottlenecks.
Material Transfer Tape (MTT) #
Material Transfer Tape (MTT)
Concept #
Transparent adhesive tape used to lift trace evidence such as fibers or hairs.
Explanation #
Pressed onto a surface, the tape adheres particles that are then examined under a microscope.
Example #
Using MTT to collect hair strands from a victim’s clothing.
Practical application #
Provides a non‑destructive method for gathering minute evidence.
Challenges #
Over‑application can embed the sample too deeply, making later extraction difficult.
Microspectrophotometry (MSP) #
Microspectrophotometry (MSP)
Concept #
Analytical technique that measures light absorption of a microscopic sample.
Explanation #
Determines the composition of pigments, fibers, or inks by their spectral signature.
Example #
Comparing the MSP profile of a paint chip to a known automotive paint database.
Practical application #
Differentiates visually similar materials for source attribution.
Challenges #
Requires highly specialized equipment and skilled interpretation.
Modus Operandi (MO) #
Modus Operandi (MO)
Concept #
The characteristic method or pattern a perpetrator uses to commit crimes.
Explanation #
Helps investigators link multiple incidents to a single offender.
Example #
A burglar who always disables security alarms before entry.
Practical application #
Guides investigative focus and resource allocation.
Challenges #
Offenders may change tactics, and overlapping MOs can create false connections.
Mounting Medium #
Mounting Medium
Concept #
Substance used to preserve and adhere microscopic samples onto slides.
Explanation #
Provides optical clarity and prevents sample distortion.
Example #
Using Canada balsam to mount a hair shaft for comparison.
Practical application #
Ensures long‑term stability of specimens for repeated analysis.
Challenges #
Incompatible mediums can cause fading or chemical reactions with the sample.
Multidisciplinary Team (MDT) #
Multidisciplinary Team (MDT)
Concept #
Group of professionals from various forensic specialties collaborating on a case.
Explanation #
Combines expertise such as DNA analysts, toxicologists, and digital forensics to enhance investigation outcomes.
Example #
An MDT reviewing a homicide case includes a pathologist, ballistics expert, and forensic psychologist.
Practical application #
Provides comprehensive insight and reduces investigative blind spots.
Challenges #
Communication barriers and differing priorities may hinder coordinated effort.
Near‑Infrared (NIR) Imaging #
Near‑Infrared (NIR) Imaging
Concept #
Use of NIR wavelengths to detect substances that reflect or absorb infrared light.
Explanation #
Reveals hidden stains, such as semen or urine, that are not visible under normal lighting.
Example #
Capturing a NIR image of a mattress to locate invisible blood spots.
Practical application #
Increases detection of trace evidence, especially on dark fabrics.
Challenges #
Requires calibrated equipment and may produce artifacts if ambient light is uncontrolled.
Neutron Activation Analysis (NAA) #
Neutron Activation Analysis (NAA)
Concept #
Non‑destructive analytical technique that determines elemental composition by measuring gamma radiation after neutron exposure.
Explanation #
Provides precise identification of trace elements in glass, soil, or metal.
Example #
Matching glass fragments from a crime scene to a suspect’s vehicle windshield.
Practical application #
Offers high discrimination power for source attribution.
Challenges #
Requires access to a nuclear reactor and specialized facilities, limiting routine use.
Non‑Destructive Testing (NDT) #
Non‑Destructive Testing (NDT)
Concept #
Examination methods that preserve the original condition of evidence while gathering data.
Explanation #
Includes techniques like X‑ray radiography, CT scanning, and Raman spectroscopy.
Example #
Using CT scanning to visualize internal bullet paths in a recovered firearm.
Practical application #
Allows investigators to examine evidence without altering it for later re‑analysis.
Challenges #
Equipment cost and need for specialized training may restrict deployment.
Officer‑Involved Shooting (OIS) Investigation #
Officer‑Involved Shooting (OIS) Investigation
Concept #
Formal inquiry into a police shooting to determine legality and appropriateness.
Explanation #
Involves collecting ballistic evidence, autopsy reports, and witness statements.
Example #
Recovering spent shell casings and analyzing trajectory to assess officer actions.
Practical application #
Provides transparency and accountability in law‑enforcement operations.
Challenges #
High public scrutiny and potential conflicts of interest require meticulous documentation.
Optical Microscopy #
Optical Microscopy
Concept #
Use of visible light and lenses to magnify small samples for examination.
Explanation #
Allows observation of morphology, texture, and color of trace evidence.
Example #
Examining fiber cross‑section under a microscope to determine weave pattern.
Practical application #
Fundamental tool for many forensic disciplines.
Challenges #
Limited resolution for sub‑micron particles; preparation must avoid contamination.
Paraben Testing #
Paraben Testing
Concept #
Chemical assay to detect presence of common preservatives used in cosmetics and personal care products.
Explanation #
Identifies trace amounts that can link a suspect’s clothing to a crime scene.
Example #
Detecting parabens on a victim’s clothing suggesting contact with a specific shampoo brand.
Practical application #
Provides associative evidence when DNA is insufficient.
Challenges #
Parabens are ubiquitous, potentially leading to non‑specific associations.
Patterned Evidence #
Patterned Evidence
Concept #
Items that exhibit distinctive designs or markings serving as class or individual characteristics.
Explanation #
Includes items such as tire tread, fabric weave, or tool marks.
Example #
Matching a specific tire tread pattern to a suspect’s vehicle.
Practical application #
Helps narrow suspect pools based on unique features.
Challenges #
Wear, damage, or environmental exposure can obscure patterns.
Photogrammetry #
Photogrammetry
Concept #
Technique of deriving measurements from photographs to reconstruct three‑dimensional objects.
Explanation #
Uses overlapping images to create a scaled model of a scene or object.
Example #
Reconstructing a blood spatter pattern using photogrammetric software.
Practical application #
Allows investigators to visualize and analyze spatial relationships without physical intrusion.
Challenges #
Requires high‑quality images and calibrated equipment; errors in scaling can affect accuracy.
Plasticine Model #
Plasticine Model
Concept #
Soft modeling material used to simulate injuries or weapon positions for courtroom demonstration.
Explanation #
Allows recreation of wound trajectories or bullet paths in a tactile form.
Example #
Building a plasticine replica of a skull to illustrate impact location.
Practical application #
Enhances juror understanding of complex forensic concepts.
Challenges #
Must be scientifically accurate; artistic bias can mislead.
Polymerase Chain Reaction (PCR) #
Polymerase Chain Reaction (PCR)
Concept #
Molecular technique that amplifies specific DNA segments to detectable levels.
Explanation #
Enables analysis of minute or degraded samples by creating many copies of target regions.
Example #
Amplifying a STR locus from a touch DNA sample on a door handle.
Practical application #
Increases the sensitivity of forensic DNA testing.
Challenges #
Contamination can lead to false positives; requires strict laboratory controls.
Presumptive Test #
Presumptive Test
Concept #
Initial screening assay that indicates the possible presence of a substance, requiring confirmatory analysis.
Explanation #
Provides rapid results but may be affected by cross‑reactivity.
Example #
Using the Kastle‑Meyer test to indicate blood, followed by spectrophotometric confirmation.
Practical application #
Guides investigators on which samples merit full laboratory work.
Challenges #
False positives or negatives can misdirect resources.
Probative Value #
Probative Value
Concept #
The ability of evidence to prove or disprove a fact in question.
Explanation #
Evidence with high probative value significantly influences the determination of truth.
Example #
A video showing a suspect entering a building has strong probative value for presence.
Practical application #
Helps judges decide whether evidence should be admitted.
Challenges #
Balancing probative value against potential prejudicial effect.
Quality Assurance (QA) #
Quality Assurance (QA)
Concept #
Systematic processes ensuring that forensic work meets established standards.
Explanation #
Involves internal audits, proficiency testing, and documentation of procedures.
Example #
A lab’s QA program includes monthly blind proficiency tests for DNA analysts.
Practical application #
Maintains credibility and reliability of forensic results.
Challenges #
Continuous updating of standards and resource allocation.
Rapid DNA #
Rapid DNA
Concept #
Automated platforms that generate DNA profiles within hours, often at the point of collection.
Explanation #
Integrates extraction, amplification, and detection in a single instrument.
Example #
Producing a DNA profile from a cheek swab at a crime scene within 90 minutes.
Practical application #
Accelerates suspect identification and reduces backlog.
Challenges #
Limited loci compared to full laboratory analysis and higher cost per sample.
Reference Sample #
Reference Sample
Concept #
Known specimen collected for comparison with unknown evidence.
Explanation #
Typically obtained from a suspect, victim, or database.
Example #
A buccal swab from a suspect used to compare against crime‑scene DNA.
Practical application #
Provides a direct basis for matching or exclusion.
Challenges #
Must be collected under proper chain‑of‑custody to avoid contestation.
Rogue Evidence #
Rogue Evidence
Concept #
Unusual or unexpected items found at a scene that may hold investigative significance.
Explanation #
Items not directly linked to the primary crime but potentially informative.
Example #
Discovering a unique keychain that matches a suspect’s known possessions.
Practical application #
Can open new investigative leads.
Challenges #
Determining relevance without causing bias or contaminating the primary evidence.
Sample Integrity #
Sample Integrity
Concept #
Preservation of an evidence item’s original state from collection through analysis.
Explanation #
Ensures that the sample’s physical, chemical, and biological properties remain unchanged.
Example #
Storing a tissue sample at -80 °C to prevent enzymatic degradation.
Practical application #
Guarantees that analytical results reflect the original condition.
Challenges #
Environmental fluctuations and handling errors can compromise integrity.
Scene Documentation #
Scene Documentation
Concept #
Comprehensive recording of a crime scene using photographs, sketches, notes, and video.
Explanation #
Captures spatial relationships, evidence locations, and contextual details.
Example #
Taking a 360‑degree panoramic photo of a burglary scene.
Practical application #
Provides a permanent visual record for later review and courtroom presentation.
Challenges #
Time pressure and lighting conditions may limit thorough documentation.
Serial Number Identification #
Serial Number Identification
Concept #
Determining the unique identifier assigned by manufacturers to equipment or weapons.
Explanation #
Involves locating and recording the number from frames, barrels, or parts.
Example #
Matching a recovered rifle’s serial number to a purchase receipt.
Practical application #
Links a specific item to a suspect or location.
Challenges #
Serial numbers may be filed, removed, or defaced, requiring forensic techniques such as acid etching.
Shotgun Wadding Analysis #
Shotgun Wadding Analysis
Concept #
Examination of the plastic or paper material that follows a shotgun projectile to infer distance and weapon characteristics.
Explanation #
Wadding size, shape, and deformation provide clues about the shot’s origin.
Example #
Identifying a unique wadding pattern that matches a specific shotgun brand.
Practical application #
Helps reconstruct shooting distance and weapon type.
Challenges #
Wadding may be destroyed upon impact, limiting recoverable evidence.
Silhouette Method #
Silhouette Method
Concept #
Visual technique for estimating the shape and size of an object based on its outline.
Explanation #
Used when detailed measurements are unavailable, allowing approximate reconstruction.
Example #
Sketching a suspect’s silhouette from a surveillance image to aid identification.
Practical application #
Provides an initial visual aid for investigators.
Challenges #
Subjectivity and lack of scale can reduce accuracy.
Simulated Evidence #
Simulated Evidence
Concept #
Artificially created items used for training, testing, or proficiency assessment.
Explanation #
Replicates real evidence characteristics without compromising actual case material.
Example #
Fabricating a bloodstain pattern for a forensic training exercise.
Practical application #
Enables skill development while preserving authentic evidence.
Challenges #
Must closely mimic real conditions to be effective; over‑simplification can mislead trainees.
Skinning Technique #
Skinning Technique
Concept #
Method for separating layers of tissue to isolate specific forensic material, such as hair or blood vessels.
Explanation #
Involves careful incision and removal of targeted structures.
Example #
Removing epidermal layers to extract hair follicles for DNA analysis.
Practical application #
Allows focused sampling without contaminating surrounding tissue.
Challenges #
Requires precision; improper technique can destroy the target material.
Spatter Analysis #
Spatter Analysis
Concept #
Study of blood or other fluid droplets to determine origin, angle, and force of impact.
Explanation #
Uses geometry and physics to interpret patterns on surfaces.
Example #
Calculating the angle of impact from an elliptical bloodstain to locate the source.
Practical application #
Helps reconstruct events such as assaults or shootings.
Challenges #
Complex patterns, overlapping stains, and surface irregularities can complicate interpretation.
Standard Operating Procedure (SOP) #
Standard Operating Procedure (SOP)
Concept #
Written instructions detailing how specific tasks should be performed to ensure consistency.
Explanation #
Covers collection, preservation, documentation, and analysis steps.
Example #
An SOP for fingerprint dusting outlines the type of powder, application method, and lift technique.
Practical application #
Guarantees uniformity across investigators and labs.
Challenges #
Updating SOPs to reflect new technology and ensuring all personnel are trained.
Statistical Significance #
Statistical Significance
Concept #
Measure of how unlikely an observed result is due to chance alone.
Explanation #
In forensic context, it quantifies the strength of a match (e.g., DNA profile).
Example #
A p‑value of 0.000001 indicates a highly significant DNA match.
Practical application #
Assists courts in evaluating the weight of scientific evidence.
Challenges #
Misinterpretation by non‑scientists can lead to overstated conclusions.
Stratigraphy #
Stratigraphy
Concept #
Study of layered deposits to interpret chronological sequence of events.
Explanation #
Applies to outdoor scenes where soil layers reveal timing of disturbances.
Example #
Identifying a disturbed soil layer under a victim’s body to infer burial timing.
Practical application #
Provides temporal context for scene reconstruction.
Challenges #
Natural processes like erosion can blur layer boundaries.
Surface Swab #
Surface Swab
Concept #
Small absorbent material used to collect trace material from a surface.
Explanation #
Rotated across an area to pick up DNA, fibers, or residues.
Example #
Swabbing a doorknob for latent fingerprints.
Practical application #
Efficient method for gathering minute evidence without damaging the substrate.
Challenges #
Inadequate pressure or insufficient coverage may lead to low recovery rates.
Suspect Interview #
Suspect Interview
Concept #
Structured conversation with a person of interest to obtain information relevant to the investigation.
Explanation #
Conducted following legal safeguards, such as Miranda rights.
Example #
Recording a suspect’s account of events after a robbery.
Practical application #
May yield admissions, alibis, or leads for further evidence collection.
Challenges #
Interviewer bias, memory distortion, and legal admissibility concerns.
Swab Preservation #
Swab Preservation
Concept #
Methods for maintaining the stability of biological material collected on a swab.
Explanation #
Involves placing swabs in sealed tubes with buffer solution and refrigerating.
Example #
Storing a blood swab in a refrigeration unit at 4 °C until analysis.
Practical application #
Prevents degradation of DNA or proteins.
Challenges #
Delays or temperature fluctuations can compromise the sample.
Technical Report #
Technical Report
Concept #
Formal document summarizing forensic findings, methodology, and conclusions.
Explanation #
Provides detailed description of analysis performed, results obtained, and interpretation.
Example #
A forensic chemist’s report on the composition of an unknown white powder.
Practical application #
Serves as evidentiary basis for courtroom testimony.
Challenges #
Must be clear, unbiased, and adhere to legal standards for admissibility.
Temperature Mapping #
Temperature Mapping
Concept #
Recording temperature distribution across a storage area to ensure consistent conditions.
Explanation #
Uses data loggers placed at multiple points to monitor fluctuations.
Example #
Mapping a freezer’s temperature to confirm it stayed at -20 °C during evidence storage.
Practical application #
Demonstrates compliance with preservation standards.
Challenges #
Sensor failures or improper placement can give misleading data.
Trace Evidence #
Trace Evidence
Concept #
Small, often microscopic, material transferred from one object to another during contact.
Explanation #
Includes fibers, hair, glass, paint, and soil particles.
Example #
Recovering a single fiber from a victim’s clothing that matches the suspect’s jacket.
Practical application #
Provides associative links when larger evidence is absent.
Challenges #
Requires sensitive detection methods and careful handling to avoid loss.
Transfer Package #
Transfer Package
Concept #
Secure container used to transport evidence between locations while maintaining chain of custody.
Explanation #
Often includes insulated compartments, temperature controls, and sealed locks.
Example #
A hard‑sided case with RFID tracking used to ship a DNA sample to a federal lab.
Practical application #
Reduces risk of damage, loss, or tampering during transit.
Challenges #
Cost and logistical coordination for specialized packaging.
Under‑Cover Operations #
Under‑Cover Operations
Concept #
Covert investigative activities conducted to gather evidence without alerting subjects