Criminalistics: Test 1

Forensic Science

Forensic Science

application of science to matters of law (criminal or civil)

Edmond Locard

Locard’s Exchange Principle: when one person comes across another person or object a cross-transfer of material occurs

When was Alabama’s forensic lab established?

1935 and it is the 2nd oldest state lab

Physical Science Unit

drugs, glass, paint, explosives, and soil

Biology Unit

DNA, Hair/fibers, botanicals (woods and plants)

Firearms Unit

Firearms, bullets, cartridge cases, shotgun shells, ammo, distance determination, and toolmarks (impression evidence)

Document Exam Unit

handwriting, typewriting, authenticity, source, paper and ink, obligation, erasures, and burned documents

Photography Unit

Examines and records physical evidence. uses specialized photography technology (IR, UV, PWL) Prepares documents for court

Toxicology

Examines body fluids for drugs and poisons including alcohol

Fingerprint Unit

examines evidence for latent fingerprints

Polygraph Unit

used mostly by a trained interrogator, not forensic scientists

Voiceprint Analysis Unit

Voice can be a fingerprint and unique to user

Crime Scene Investigation Unit

Document and collect evidence that will be processed later at crime lab

Fyre v. United States

Scientific examination procedure must be generally accepted within the scientific community

Daubert v. United States

Has the technique or theory been tested, has there been peer review, rate of error, are there standards controlling the techniques operation, has this technique attracted widespread acceptance within a relevant scientific community.

6 Step Methodology for working a crime scene

1) assess- gather resources and information

2) observe- walk through the scene, locate primary focal points, exit/entry points, secondary scene

3) Document-Notes, photograph, sketch, measure “fixed items”

4) Search- look for evidence

5) collect- using PPE, and clean bags/containers, place items in and seal

6) analyze- use chemicals, powders, road mapping at the scene, and analyze at the lab

4 types of Photographs

1) general photos

2) evidence establishing shots (mid-range shots)

3) close up shots

4) Forensic Quality photos

general photos

show the basic layout of the scene, usually from the 4 corners. uses an undistorted lens. document without visual bias

Evidence Establishing Shots (mid-range shots)

shows item of interest along with a fixed object; use placecards; remember isosceles

Close Up Shots

Usually don’t need a scale/ruler, but you want to fill the frame and get as much data in the photo

Forensic Quality Photos

Always be ISO 100, tripod used with trigger release, camera’s digital sensor plane parallel to object and a scale to show precise size

Good Compisition

part art and part knowledge of what your audience needs to accurately tell a story

Isosceles Triangle

Photographer stands equal distant from the fixed point and the item of interest. Establishes true distance of objetcs (Body parts (that are not going to move on their own) can be fixed points)

Metering

shows if the shot is under or over exposed. If the meter is at 0, the shot is at a good exposure

Bracketing

Purposefully under or over exposing photos

Shutter Speed

“click”; most forensic work requires slower shutter speeds, due to low levels of ambient light at a typical crime scene

F-stop

Change the depth of field, F2-F22, most scene can use F11 ,but forensic scientist need high Depth of Field

Tiny Aperture

has less light but a large depth of field (F22)

Large Aperture

has more light but small depth of field (F2)

ISO

Light sensitivity, Forensics uses ISO 100, the higher the ISO level the more grainy the photo is

Class Characteristics

Evidence that can be associated to a group and not a single source

Individual Characteristics

Evidence that can be associated with a common source with extremely high probability

How do you compare evidence?

You use the same tests to test the unknown and known samples and compare the results

Identification

determine the physical/chemical identity of a substance with as near absolute certainty based on the analytical techniques (Remember Frye or Daubert)

Fingerprint Database

Integrated Automated Fingerprint Identification System

DNA Database

Combined DNA Index System

Genealogy Databases

GEDmatch, 23andme, and ancestry.com

Ballistics Database

National Integrated Ballistics Information Network

Paint (car) Database

International Forensic Automotive Paint Data Query

Shoeprint Database

Shoeprint Image Capture and Retrieval

When does physical evidence achieve its optimal value?

when its collection is performed with a selectivity governed by the collectors thorough knowledge of the crime lab’s techniques, capabilities, and limitations

1. Secure and Isolate the Crime Scene

The first responder has a major job: they need to preserve and protect the crime scene as much as possible, take care of any hazards or dangers, look for anyone coming or going from the scene, look for a victim, minimize the amount of people at the scene and call EMT if needed, take preliminary photos. Main investigator can start assessing the scene, look for entry/exits points of the perpetrator, and determine the boundaries.

Scene context manifested in 5 ways

1. Predictable Effects

2. Unpredictable Effects

3. Transitory Effects

4. Relational Detail

5. Functional Detail

Predictable Effects

Changes to the scene or evidence that follows a rhythm or regularity, like entomological activity or liver or rigor mortis

Unpredictable Effects

Changes that occur randomly or in an unexpected fashion. EMT or police disrupting a scene or evidence. This can be disastrous because it can alter the evidence and scene is lost forever.

Transitory Effects

Temporary effects during a crime scene. Odors, temperature, ice in a glass, cigarette burning. Fleeting pieces of information that eventually will be lost due to time and environment. First responders are trained to look for such items.

Relational Detail

Manifests itself to the ability of the investigator being able to physically place items in a scene. Presence of a void on a wall, cluster of casings on the grass, recognizing short vs. long distance gunshot wound. Evidence outside could be easily moved by the wind, so measuring all items is crucial inside or outside a scene.

Functional Detail

the item/s involved in the crime able to perform normally. Was gas functional, was door bolt functional, was alarm on. Each tells the investigator what was possible or impossible.

2. Recording the crime scene: Documentation

Recording with documentation the scene provides a way to permanently record the scene in its original state. Note time, date, who is there, interview the first responder and what context changed, lead investigator does an initial walkthrough and takes notes, mark locations of evidence, and describe things that photo can’t record.

3. Conducting a Systematic Search for Evidence

done by CSI not forensic scientists (typically

Strip or line search pattern

good when you know the boundary

Grid Search pattern

good when you know the boundary (double line search)

Spiral Search Pattern

good for smaller areas, work your way in or out

Wheel or Ray search pattern

work in or outward, but not commonly uses

Quadrant or zone search pattern

divides the area into smaller sections, one section per team member. Can be used for car sections

4. Collecting and Packing Physical Evidence

Can be full cars, airplanes, or trace amount of evidence like hair. Clothing must be handled carefully and wrapped separately to avoid loss of trace evidence (hairs, fibers, blood transfers). Vacuum and sweeping must be collected separately each from different areas (sweeping drivers side vs. passengers side). Pill boxes/bottles are good for trace evidence. A druggist fold is good for trace evidence too. Plastic bags and envelops are good for small objects that are dry. While large paper bags are good for items that need to breath like blood evidence. Can place very bloody evidence into a plastic container for short periods and in cold environment until transportation to lab drying cabinet can be done. Arson cases use metal “clean” paint cans, that can be sealed, as to not let out volatiles.

Maintaining the Chain of Custody

Continuity of possession. who had the evidence and where was it located during every step of the process. from collection at the scene, to locker, to lab personnel, to returning back to the police department must all be accounted for. Initial and date the tape seal of the container.

Standard/Reference Samples

known piece of evidence that can be compared to item/substance found at scene