crime scene investigation

Crime Scene

Any physical location in which a crime has occurred or is suspected to have occurred

Primary Crime Scene

The original location where a crime or accident occurred

Secondary Crime Scene

Alternate location where additional evidence related to the crime may be found

Suspect

A person thought to be capable of committing a crime

Accomplice

A person associated with someone suspected of committing a crime

Alibi

A statement of where a suspect was at the time of a crime

Police Officers

First responders who secure the scene and detain individuals

CSI Unit

Documents the crime scene and collects physical evidence

District Attorney

Determines if search warrants are needed and obtains them from a judge

Medical Examiner

May be present to determine preliminary cause of death

Specialists

Experts like entomologists, anthropologists, psychologists who analyze specific evidence

Detectives

Interview witnesses, consult with CSI, follow leads and physical evidence

Crime Scene Protocol Step 1

Interview

Crime Scene Protocol Step 2

Examine

Crime Scene Protocol Step 3

Document

Crime Scene Protocol Step 4

Process

Fingerprint Principle 1

Fingerprints are unique; no two individuals share the same pattern

Fingerprint Principle 2

Fingerprint patterns remain unchanged throughout life, except due to scars/diseases

Fingerprint Principle 3

Fingerprints have general ridge patterns that can be systematically classified

Impression Evidence

Marks left when one object is pressed against another with enough force

Examples of Impression Evidence

Shoeprints, tire tracks, bite marks, tool marks, fired bullet markings

Factors Affecting Impressions

Object characteristics and surface conditions (e.g. soil, dust, skin)

Serology

Lab tests using antigen-antibody reactions to identify blood types

Blood Group Identification

Test with anti-A and anti-B sera to classify A-B-O groups

Forensic Blood Questions

Is it blood? What species? Can it be linked to a specific individual?

Preliminary Blood Test

Kastle-Meyer color test for blood detection

Forensic Pathologist Role

Collect medical evidence, perform autopsies, reconstruct cause of death

Forensic Pathologist Training

Includes toxicology, ballistics, DNA, serology, wound and trace analysis

Y-Incision

Standard incision method used in autopsies

Coroners vs Medical Examiners

Coroners may lack medical training; medical examiners are trained physicians

Post-Mortem Exam

Internal & external investigations; samples collected and examined microscopically

Clinical/Pathological Autopsy

Performed to identify disease as cause of death, with family consent

Medico-Legal Autopsy

Used in unnatural deaths; conducted by forensic expert

Anatomical Autopsy

Performed by students to study human anatomy

Medical Examiner Tasks

Investigate sudden deaths, consult, testify in court, run tests, issue subpoenas

DNA Analysis Use

Identifies individuals in crimes by comparing DNA to forensic databases

Forensic DNA Samples

Blood, semen, saliva, hair, skin, sweat, urine, nasal/vaginal secretions

Polymorphisms

Individual DNA variation allowing unique identification

DNA Analysis Techniques

RFLP, PCR, AmpFLP, Mitochondrial DNA, Y-chromosome analysis

Forensic Toxicology

Study of poisons and drugs; determines presence and quantity in the body

Ballistics

Study of projectile motion inside, outside, and impact phase of firearms

Firearms Identification Principle

Harder objects transfer microscopic marks to softer ones

Firearms Expert Tasks

Bullet comparison, function testing, serial number restoration, residue detection

Osteology in Forensics

Study of bones to build biological profile of deceased

Anthropologist Tasks

Estimate age, sex, ancestry, stature, trauma, and possible cause of death

Skeletal Trauma Analysis

Determines injury type, timing, and potential weapon used

Young vs Adult Skeletons

Epiphyseal union and teeth development help estimate age

Tooth Analysis

Used to estimate age between 5 months to 21 years (baby vs permanent teeth)

Height Estimation

Rule

Ethnicity from Bones

Facial structures (nose, eye sockets) help infer ancestry

Gender from Pelvis

Female pelvis is wider than male pelvis

Forensic Facial Reconstruction

Recreates face from skull using artistic and anatomical methods

Facial Reconstruction Types

2D drawings, 3D clay/computer models, photographic superimposition

Circumstantial Identification

Based on match between skeletal remains and biological profile

Positive Identification

Requires dental/medical records, DNA, or unique prior injuries/pathologies

Antemortem

Before death

Perimortem

At or near time of death

Windows Hello Step 1

Detect face and locate alignment points (eyes, nose, mouth)

Windows Hello Step 2

Check head orientation to ensure face is within 15° angle

Windows Hello Step 3

Build facial representation vector using thousands of samples

Windows Hello Step 4

Compare representation to enrolled users, accept if above threshold

AI for Earth

Uses AI and cloud tech to identify endangered species

Wildbook

Uses computer vision and deep learning to identify individual animals

Sewer Sensors

Used to detect bombs and drugs through chemical signatures

Virtual Autopsies

Non-invasive body exams used in the UK, US, Japan, and Australia

Lumicyano Technique

Amplifies trace DNA from sweat/hair by skipping extraction step

China’s LAC Presence (2024)

PLA maintains 1.2 lakh troops and artillery despite disengagement claims

China’s Military Modernization

Expanding