Crime Scene Processing

What is crime scene processing

an examination and evaluation of the scene for the purpose of recovering physical evidence and documenting the scene as found

Types of crime scenes

outdoor, indoor, conveyance

Outdoor crime scene

most vulnerable to loss and contamination of evidence / need to ensure it’s properly secured / fragile evidence

Indoor crime scene

less susceptible to loss and contamination / easier to protect

Conveyances

form of transportation / evidence may extend beyond the vehicle

Challenges with outdoor crime scenes

contamination of evidence, weather, animals, people, movement of evidence, fragile evidence

Challenges with indoor crime scenes

hard to identify what is a part of the crime and what isn’t

Challenges with conveyance crime scenes

it moves, evidence can extend beyond the vehicle, things can be thrown out, hard to distinguish what is a part of the scene and what is not

Crime scene investigation team

police officers, crime scene investigators, medical examiners, detectives, specialists, laboratory scientists

Objectives of first responders

document provided info, not become a casualty, provide for emergency care, secure and control the scene and all those within it, release the scene to the appropriate authorities

Fourth amendment

“the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches or seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized”

Search warrants

court order, issued by a judge or magistrate to authorize law enforcement officers to search a person, location, or vehicle for evidence and to confiscate that evidence

Exceptions to search warrants

consent, plain view, exigent circumstances, hot pursuit, search incident to an arrest

6 basic steps in processing a crime scene

assessment, observation, documentation, searching, collecting, analyzing

Assessment

what type of crime if any was committed, how extensive is the scene, what resources will you need, are there any risks inherent to the scene

Observation

what do you see, is there evidence of a crime, what type of evidence is there to collect, primary vs. secondary crime scenes

Primary crime scene

where the crime actually happened

Secondary crime scene

other places related to the crime

Documentation

how will you record the scene / notes, photography, videotaping, sketches

Searching

how will you search, who will search, what are you searching for / starts to be intrusive / are there ever any searches after the initial search

Area approach to searching

a single team handles all activities associated with processing / group documents its area of the scene and searches for and collects evidence / typical in small police departments

Function approach to searching

team leader designates different teams to do different activities / ex: documentation team or fingerprint team / more important is the order the team processes vs who does what

Search considerations

must be methodical and systematic / nature of the ground being searched, lighting conditions, on scene environmental conditions, size of the item being searched for

Most common search patterns in US

circle or spiral search, strip and line search, grid search, zone search

Circle or spiral search

effective in interior scenes / can start at the outer edge and work your way in or process in reverse / must be aware of the pace of the search

Strip and line search

often used in exterior scenes for large areas / typically a line search has a number of searchers / must ensure you move the group together as one

Grid search

divides the area into two sets of strips or lanes that run at 90 degree angles to one another / creates a second look at the scene

Zone search

most effective when dealing with small confined spaces / subdivision of large scene into smaller manageable pieces

Collecting

what will you collect, how will you collect it, who will collect it / always intrusive / once an item is moved, context is forever altered / what about fragile evidence

Content

the evidence

Context

clarifies the meaning of the evidence

Documentation of evidence

date/time of collection, name of person collecting evidence, description of items collected, unique identifier, location of item

Chain of custody document

document that maintains integrity of evidence

Collection techniques

photograph first / collect, package, and seal items individually / collect fragile evidence first / each type of evidence may require its own type of packaging

Processing + analyzing

what needs to be analyzed, who will do the analysis, what should be analyzed first

Evidence

can be anything that helps support or refute a fact in contention (testimonial or physical)

Testimonial evidence

collected through interview and interrogation of witnesses, victims, and suspects / helps to understand motives or explain items found at the scene

Physical evidence

takes the form of specific items found at the scene that are often collected for subsequent analysis and presentation / may not be collected but simply documented

Circumstantial evidence

suggest occurrence of possible events

Direct evidence

allows for conclusions of indisputable facts or evidence

Class evidence

narrows an identity to a group of individuals

Individual evidence

narrows an identity to a single person or thing

Class characteristics

most useful for eliminating possibilities / can include things like size, color, common manufacturing patterns

Individual characteristics

unique characteristics resulting from natural variation, damage, or wear / powerful evidence to conclusively state that the evidence is derived from something specific / context is crucial for the value of evudence

Locard’s principle of exchange

every contact leaves a trace / criminal leaves something behind at a scene and takes something with them

Theory to trace evidence

direct or indirect transfer

Forensic evidence triangle

subject to victim to scene back to subject (all connected)

How to evaluate evidence

what is it and what function did it serve, what relationship does it have to any other items of evidence or to the scene itself, what does it tell us about timing and sequence aspects

Physical evidence manifestations

predictable, unpredictable, transitory / relational details, functional details

Predictable changes to evidence

changes to the scene or evidence that occur with some rhythm or regularity / such evidence provides investigator a factual reference or inference to actual time of the crime

Unpredictable changes to evidence

changes that occur in an unexpected or random fashion / important because if it’s not recognized, it could cause misinterpretation of the evidence

Transitory effects to evidence

often these are fleeting effects / must take good notes of what is observed upon your arrival / only through deliberate observation that transitory effects are noted

Relational details

investigators ability to physically place items in the scene / ex: void pattern on a wall surrounded by spatter, clustering of shell casings on grass, presence of weapon close to the victim

Functional details

operating condition of items in the scene / ex: weapon capable of operating in a normal fashion, alarm clock set for a specific time, did deadbolt operate normally

Timing

allows us to place the time of the crime

Sequencing

helps us to decide how or in what order the crime occured

Scene integrity occurs

the addition of material to the scene, the destruction of material in the scene, the movement of material in the scene

Addition of material

post-incident artifacts / creation of evidence that was not there to begin with / can observe the investigator’s understanding of the crime and can be used by defense counsel to cast doubt for the jury / locard’s principle

Destruction of material

loss of an item’s evidentiary value

Movement of material

often the result of investigative processing techniques / when unrecognized, it can cloud the investigator’s understanding of the crime scene / significantly changes the relational aspect observed by the investigator