Ch. 1 Crime Scene Investigation of Biological Evidence

What is the initial response for a first responding officer at a scene?

Secure and protect the scene.

What personal protective equipment (PPE) should be used to prevent contamination at a scene?

Face mask, safety glasses, disposable coverall, gloves, shoe covers, hairnet.

What type of evidence is given the highest priority?

Evidence related to corpus delicti.

What does corpus delicti mean?

“Body of crime” — physical evidence proving that a crime was committed.

What is victim-to-perpetrator linkage?

Items found on the perpetrator that may be linked to the victim.

What does the Locard exchange principle state?

Transfer of evidence occurs when a perpetrator has physical contact with an object or person.

What indicates a victim-to-scene or perpetrator-to-scene linkage?

Victim or perpetrator’s blood found at the crime scene and cross transfer of trace evidence.

What is case-to-case linkage?

Evidence of a unique modus operandi (MO).

What search patterns are useful for large, outdoor crime scenes?

Grid, line, or zone search patterns.

What is an Alternate Light Source (ALS)?

A device that produces specific wavelengths of light using filters.

• Blood, semen, and saliva.

What are field tests and enhancement reagents described as?

Simple, rapid, and sensitive.

Which reagents are used for detecting blood in field tests?

Phenolphthalin and leucomalachite green.

• Luminol and fluorescein

What is the purpose of luminol and fluorescein in blood detection?

To detect traces of blood not visible to the naked eye.

What must be documented at a crime scene and why?

Conditions of both individual items of evidence and the overall scene; this information is vital for investigators and courts.

What types of documentation methods are used at a crime scene?

Sketches, photographs, videos, written notes, and audio notes.

What do sketches show at a crime scene?

Positions and spatial relationships of evidence.

What types of photographs should be taken and what should they include?

Overall, mid-range, and close-up photos including a measuring device and close-ups with a scale.

What is the chain of custody?

Custody information recorded every time evidence is handled or transferred.

What type of evidence requires especially thorough documentation?

Bloodstain pattern evidence.

How should evidence be analyzed?

Multiple analyses may be done, starting with nondestructive tests first.

What is important to remember about trace evidence in bloodstained samples?

Trace evidence can be present and should be properly collected and sealed.

How should wet evidence be handled?

It must be air-dried (no heat) to prevent degradation of proteins and nucleic acids.

Why is marking evidence necessary?

For identification, even years later.

What information should be included when marking evidence?

Investigator’s initials, item number, date, and case number.

How can evidence be marked?

Directly on the item or on an attached label.

What is the purpose of proper packaging and transportation of evidence?

To preserve evidence and protect it from contamination.

What type of packaging material should be used for biological evidence?

Porous materials to allow airflow and prevent mold or degradation.

What are the final steps before releasing a crime scene?

• Conduct final survey

• Review all aspects of the search with all personnel at the scene

• Ensure all documentation is complete

• Confirm all evidence is collected, packed, documented, and marked

• Photograph the final condition of the scene

When can a crime scene be officially released?

Once the final survey and documentation are complete, and all evidence is collected and photographed.

What is crime scene reconstruction?

The scientific process of determining the sequence of events and actions before, during, and after a crime.

What is crime scene reconstruction based on?

Information from crime scene observation and laboratory examination of physical evidence.

What are the steps involved in crime scene reconstruction?

1. Identify problems to be solved

2. Collect useful information

3. Construct hypotheses

4. Make predictions based on hypotheses

5. Test the reconstruction

6. Analyze data and draw conclusions