7 S's of Crime Scene Investigation, Types of Evidence, Collecting Evidence

What is the very first responsibility of the 1st Officer to arrive on the Crime Scene?

see if victims need medical assistance

Once the 1st officer has seen if the victim needs medical assistance, the next thing they need to do is?

search for & arrest suspect if they are present at the scene

The last thing the 1st officer does in the Secure Step

secure the scene with barrier tape and place officers at a common approach (enter and exit the crime scene)

Every person who enters and exits the crime scene must be documented on what?

Crime Scene Entry Log

What must be documented on a crime scene entry log?

the date, time, and name of every person who enters & exits the crime scene

What is the second step in crime scene investigation?

separate the witnesses

Why should witnesses be separated?

so that they do not influence each other AND to avoid collusion

What happens during the third step in crime scene investigation?

Scan the scene- do a walkthrough and look for transient (temporary evidence) and mark all evidence found with evidence markers

What is occurring during step 4, seeing the scene?

evidence is being documented, photographed, from several angles & distances with a scale

What is the main rule about preservation of evidence?

it must be preserved in its original state

Charred/burned debris should be packaged

in an airtight container

Bloody clothing should be packaged in

paper bags to dry off and avoid the growth of mold

Can multiple items of evidence be placed in the same evidence container?

no- all pieces of evidence must be packaged alone to prevent cross-contamination

Can evidence only be found at the crime scene?

no- there may be multiple crime scene locations, also evidence may be found on a victim

What is the chain of custody?

a process whereby evidence is accounted for from the moment it was collected to the moment it is presented in court

If there is a break in the chain of evidence, can that evidence be used in a criminal proceeding?

no- it will be inadmissible

All evidence containers must be sealed with tape and...?

the tape must have a signature on it of the collecting officer, it must also have a chain of custody log that travels with the evidence at all times

How should CSI package very small, trace, evidence, such as hairs and fibers?

(a paper bindle, which is then packaged in a plastic evidence bag, both the bindle and the bag are sealed with evidence tape

Define primary, secondary, and tertiary crime scenes

primary= 1st, secondary is a second location, tertiary are all additional scenes associated with the crime

What is Locard's exchange principle?

every contact leaves a trace

What is direct evidence & give an example?

Direct evidence proves a fact directly without any inference or presumption. If the evidence is true then the fact is conclusively established. For example: witness testimony that the witness saw it raining outside before he came into the courthouse. That testimony by the witness is direct evidence that it was raining. (first-hand observations, examples: eyewitness accounts, police dashboard, video surveillance, voice recordings, signed ransom notes, lab reports)

What is circumstantial evidence & give an example

indirect evidence that can be used to imply a fact, but not directly prove it, examples: fingerprints, DNA, ballistics, hairs, fibers

What are two types of circumstantial evidence?

physical and biological

Biological Evidence

body fluids, hair, plant parts, natural fibers

Physical Evidence

Any object that can establish that a crime has been committed or can link a crime and victim or perpetrator. shoe prints, fingerprints, weapons.

Transient Evidence

temporary; easily changed or lost; usually observed by the first officer at the scene (odor, temperature)

class evidence

material that connects an individual or thing to a certain group (blood type)

individual evidence

a kind of evidence that identifies a particular person or thing (DNA, fingerprints)

reference sample

physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene evidence

Crime scene reconstruction will help investigators

Determine how many people were involved in a crime, how the victim was killed, and if any actions were taken to cover up a crime

What is the 5th step in 7 S's of crime investigation?

Sketch (rough and final)

What is the 6th step of the 7 S's of crime investigation?

Search

• spiral

• grid

• line

• zone

What is the 7th step of the 7 S's of crime investigation?

Secure & collect evidence

footprints/ tire impressions

photos and casts (for project, just photograph & say you will cast it on the video.

trace evidence

(hairs, fibers, soil, paint chips): placed in a bindle & then a plastic evidence bag. Fragile into rigid containers (like a box)

documents

Collected in plastic or cellophane envelopes

ballistics

you will have a picture- but explain that bullets are collected with tweezers and placed in a small box, Gun: all bullets removed from the gun and put into their own bag, the gun itself is put into a special box to prevent it from firing.

tools

working end of the tool is wrapped in cloth to prevent damage and loss of trace evidence and placed in a box or bag.

toolmarks

Photographed first, if small entire item collected. If large a silicone cast is made of the impression.

blood & bodily fluids

are dried and put in a paper bag to prevent the loss of evidence due to decomposition.

Accelerants/Ignitible Liquids

items with accelerants are placed into airtight containers (metal paint can or glass) to prevent evaporation.

fingerprints

fingerprint powder and brush are used, tape is placed over the print onto a fingerprint card.

Dashboard Camera Footage

direct evidence

Fingerprint

circumstantial- physical

gunshot residue (GSR)

circumstantial- physical

eyewitness

Direct

cotton fiber

circumstantial- biological (cotton is from a plant)

glass fragments that can be matched to a source

individual

blood types

class

shoe print from brand new shoes

class (individual if they were well worn)