Forensic science 25 unit 1 review

1 Introduction to Forensic Science

• Forensic science is the application of science to law.

• Criminalistics involves applying science specifically to criminal and civil laws enforced by police agencies.

• Interest in forensic topics has grown due to the popularity of true crime narratives in media.

History of Forensics

• Sherlock Holmes: Sir Arthur Conan Doyle popularized scientific crime-detection methods through this character, including fingerprinting and firearm identification.

• Mathieu Orfila: Known as the father of forensic toxicology; published scientific detection of poisons in 1814.

• Francis Galton: In 1892, he studied fingerprints, developing methods for classifying fingerprint patterns and providing statistical proof of their uniqueness.

• Calvin Goddard: Developed techniques for matching fired bullets to firearms using comparison microscopes.

• Advancements: Recent developments in computer technology and DNA typing have greatly enhanced forensic capabilities, allowing for precise links between criminals and crimes.

2 Basic Services Provided by Crime Laboratories

• Crime labs vary greatly in size and specialization but can typically be categorized into:

  • Physical Science Unit: Uses chemistry, physics, and geology for evidence like drugs and explosives.

  • Biology Unit: Handles blood stains, hair comparisons, and botanical materials.

  • Firearms Unit: Examines firearms, bullets, and discharge residue.

  • Photography Unit: Maintains labs for documenting physical evidence.

3 Functions of the Forensic Scientist

• The primary role involves collection and analysis of physical evidence.

• Forensic scientists apply scientific techniques while adhering to judicial system constraints.

• Expert Testimony: Forensic scientists may testify in court, providing professional opinions based on training and scientific methods. Objectivity and credibility are paramount; they advocate for truth, not any party's cause.

4 Standard Procedure for Approaching a Crime Scene

• Physical evidence is crucial for establishing links between crimes, victims, and perpetrators.

• First responders must prioritize safety and isolate the crime scene.

• Recording crime scenes involves photography, sketches, and notes, all crucial for preserving original conditions.

5 Photographing a Crime Scene

• Photographs should capture the scene before altering any evidence.

• A rough sketch is necessary for detailing object dimensions and placements; a finished sketch can be created later.

• Consistent note-taking is essential, providing detailed descriptions and crucial information about evidence collection and processing.

6 Collecting Evidence

• Common evidence collected includes victim clothing, blood samples, and hair.

• Each item must be carefully packed to prevent contamination, using separate containers for each to avoid loss or damage.

• Controls (known samples) are essential for comparison to assess the significance of collected evidence.

7 Types of Physical Evidence

• Evidence analysis follows different categories:

  • Comparison: Requires control samples for accuracy (e.g., fingerprints).

  • Visual: Unassisted observation is feasible (e.g., fingerprints).

  • Microscopic: Needs microscopes for examination (e.g., hairs, fibers).

  • Chemical: Involves chemical procedures (e.g., DNA typing).

8 Common Types of Evidence

• Documents: Handwritten or printed notes examined for authenticity. Handwriting analysis is challenging due to subtle variations.

9 Glass, Soil, and Vegetative Evidence

• Glass Fragments: Can link suspects to crime scenes; may contain prints or blood.

• Soil: Can connect a suspect to a location but usually viewed as circumstantial unless rare materials are present.

• Fingerprints: Can link a person to a crime if properly developed and analyzed.

• Hairs and Fibers: Hairs provide links via microscopic examination; fibers can identify relationships between individuals or objects.

10 Firearms and Ammunition Evidence

• Evidence from firearms is critical for convictions in shooting cases.

• Powder Residue: Indicates if a person discharged a firearm.

• Explosives: Provide valuable information regarding explosions and fires, including chemical residue.

11 Impressions and Tool Marks

• Impressions from tires, shoes, and tools can be analyzed to identify suspects.

• Databases exist for comparison to enhance investigative accuracy.

12 Drug Evidence

• Samples of suspected drugs are examined to confirm identity and strength.

• Advances in technology play a crucial role in analysis.

13 Paint Evidence

• Paint can link a suspect to crimes, especially in hit-and-run cases; control samples are necessary for analysis.

14 Blood and Biological Fluids

• Body fluids are subjected to analysis for identity and behavior prediction.

• Blood typing and DNA analysis are commonly employed.

15 Chain of Custody

• Maintain a continuous record of evidence handling to protect its integrity in court.

• The chain of custody documents each individual handling evidence to prevent defamation of its credibility.

• Class vs. Individual Evidence: Class evidence can be valuable when sufficient data links a suspect to a crime, as demonstrated in notable cases.