physical evidence and crime scene Flashcards
Crime scene scientific process
- Crime scene
- Collection and preservation of evidence
- Submission to lab
- Evaluation of results and report
- Trial
Crime scene legal process
- Crime scene
- Warrant documentation
- Investigation
- Admissibility in court
- Trial
Shifting focus of forensics and the legal aspect
- Over time, focus will shift from then lab to the scene
- The CSI process will become more important than ever before
- All the defense has to do is prove a scene was mishandled
what is evidence?
Testimony, records, documents, material objects, or other things presented at a trial to prove the existence or nonexistence of fact
evidence is the exchange of material between two persons, persons to things, or things to things
Physical evidence
Any objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator
Classifications of evidence
- Physical evidence
- Testimonial evidence
- Direct evidence
- Circumstantial evidence
- reconstruction evidence
- associated evidence
Direct evidence
- Establishes “directly” the fact of the information
Types: eyewitness, crime scene photography, ID of a powder as an illicit drug
- Does not need to infer anything regarding the evidence
Circumstantial evidence
- Can infer additional information
- Ex. Defendant’s semen is found on the victim, therefore links their DN to crime scene
- Inferring the individual was at the scene and sexual activity occurred
- but does not imply they are guilty of sexual assault
reconstruction evidence
provides information about the events preceding, occurring during, and after the commission of a crime
associated evidence
- items that are considered of unknow or questionable origin until a comparison is made to a known standard or exemplar
- helps link a person to a place
Examples of classifications of evidence
- eyewitness: testimonial, direct, and reconstruction
- bloodstain splatter: physical, circumstantial, reconstruction
- cocaine powder: physical, direct, associative
examination of physical evidence
- comparison: determining whether two or more objects have a common origin
- identification: determining a substance’s physical or chemical identity
Evidence: class characteristics
class: properties of evidence that can be associated only with a group, never with a single source
- It’s a blue car
- Fiber
- Body fluid (not DNA)
evidence: individual characteristic
Individual: properties of evidence that can be attributed to a common source with an extremely high degree of certainty
- license plate number
- DNA in a strand of hair
- Striation marks on a bullet
- Fingerprint
results of comparison
- Inclusive: include as a possible source
- Ex. The DNA from the door handle matches the DNA of the suspect
- Exclusive: not a source
- Ex. The DNA from the door handle does not match the SNA of the suspect
- Does not mean innocence, but does not mean proof either
- Inconclusive: neither include nor exclude as a possible source
- Ex. Not enough DNA was collected from the door handle
who is at the scene? (1)
- Police officers
- First to arrive
- Secure the scene
- Evidence technician or trained officer
- Document the scene
- Collect physical evidence
- District attorney (DA)
- Can help determine if a search warrant is needed
who is at the scene? (2)
- Medical examiner
- May determine cause of death (COD)
- Specialists
- May provide expert analysis
- Detectives
- Interview witnesses
- Investigate any leads
- EMT, firefighters
- Save lives FIRST
general process at a crime scene
- Secure and isolating the crime scene
- Crime scene processing
a. Preliminary survey
i. Prioritize perishable evidence
ii. Already documenting
b. Official documentation
c. Search
i. Searching for more evidence
ii. Still documenting
d. Evidence collection
i. Package and deliver evidence to laboratory - Final survey and release of the scene
The first officer on the scene should:
o Call for medical assistance or make arrests
o Secure and isolate the core area of the crime scene from unauthorized personnel
The CSI arriving on scene should first
- Evaluate the area and make sure it is secure
- Conduct an initial walk through of the scene
- Take immediate note of details
- Define extent of crime scene
- Develop a plan for examining and documenting the entire crime scene
