Physical evidence*
any object that can establish that a crime has or has not been committed, or can link a crime and its victim or perpetrator
Securing and Isolating the Crime Scene
1) the first officer arriving is responsible for preserving and protecting the area as much as possible; note any vehicles or people leaving scene
-evaluate victim's condition and record any statements
-first priority is getting medical help for people wh
The mark of a trained and professional crime-scene investigative team is...
the accomplishment of securing and isolating the crime scene, which are critical steps in an investigation.
At a crime scene, personnel should never...
do anything:
-eat, drink, adjust temperature, open windows, adjust AC, flush toilets, smoke.
Recording the crime scene
have limited time with undisturbed crime scene
-includes notes, photography, and sketches.
-useful during investigation and also required for presentation at a trial to document the condition of the crime site and delineate location of physical evidence
-
Notes
1) Call a crime-scene investigator to the scene
2) identify person who contacted investigator, time of contact, any preliminary info disclosed (case number)
3) When the lead investigator arrives, the note taker should record date and time of arrival, who'
Before the scene is sketched, photographed, or searched, the lead investigator...
...carries out an initial walk-through
-takes notes on crime scene
-write in a bound notebook, ink, at the time of the crime-scene investigation
Once a search for evidence has happened, the team...
...marks the location of all evidence and describe each in their notes.
-observe and record state of body of a victim before medical examiner/coroner moves it.
-preliminary identification of a victim/suspect should be recorded
Aside from pen and paper, these methods can also be used for note-taking.
1) tape recorder
-can be taped fast, hands free, and security feature of preventing erasure/taping over if security tab on tape's removed
2) narrating a videotape
-combines notetaking and photography
-must be transcribed eventually, though
Photography
-photos must be unaltered
-unless injured people are involved, objects must not be moved until they've been photographed.
--otherwise, photos might not be admissible as evidence at a trial.
If evidence has been moved/removed before photography...
...this fact should be noted in report, but evidence shouldn't be put back in order to take photos
The value of crime-scene photographs.
can show layout of scene, positions of evidence, relation of objects at scene to one another.
-taken from multiple angles, photos can show possible lines of sight of victims, suspects, or witnesses
-accurate description of scene must be available to inves
Two approaches to crime-scene photography
1) film
-sheet of light-reactive grains
2) digital
-microchip turns light into pixels
-mostly used
-can be easily manipulated, though
-many jurisdictions set guidelines for determining when digital photos can be used, establish and e,force strict protocol
Photographic Procedures
1) overview photos of entire scene and surrounding area, points of exit and entry, taken from many angles
-all walls if took place inside.
-adjacent rooms to crime scene also photographed like this.
2) If there's a body, must show position and location re
Video Recording: how to
1) should include entire scene and immediate surrounding area
-long shots as well as close-ups taken in a slow, systematic manner.
-have one crime-scene investigator narrate the evens and scenes being recorded while another videos.
Video recording: Pros and Cons
Pros:
-becoming increasingly cheaper, and thus more popular
-combine notes and photography
Cons:
-shakes, zoom can be sloppy.
-blurry stills.
-extra noise can obscure narration.
-if videotape is used instead of digital, it can deteriorate cuz tape is sens
Sketches
-done after photos are taken
-serves important legal functions
-can show layout of indoor or outdoor crime scene and relationship in space of all items and features
-illustrate location of collected evidence
-allows speculation of paths of entry, exit, mo
Rough Sketch
a draft representation of all essential info and measurements at a crime scene; drawn at crime scene
-accurate depiction of dimensions of scene
-location of all objects important to case
-objects located in sketch by distance measurements from two fixed p
Finished sketch
a precise rendering of crime scene, usually drawn to scale
-care taken for aesthetics
-Computer-Aided drafting (CAD) is used to reconstruct from rough sketches.
Conducting a systematic search for evidence
-thorough search for physical evidence must be conducted at once, no matter what.
-avoid accusations of negligence, charges of "covering up" evidence.
-investigator assigns those to search a crime scene
-use of forensic scientists at crime scenes usually
Search Patterns
Strip or Line, Grid, Spiral, Wheel or Ray, Quadrant or Zone search pattern.
-depends on location and size of area, actions of suspects and victims at scene
-one person should supervise and coordinate collection of evidence when possible
--avoids confusion
Strip or Line Search Pattern
Best for scenes when boundaries well established.
1)One or two investigators start at boundary at one end of scene, walk straight across to other side
2) Move a little farther along border and walk straight back to other side.
Grid Search Pattern
Two people perform line searches originating from adjacent corners, form perpendicular lines
-very thorough
-boundaries must be well established to use this method well, though
Spiral Search Pattern
Usually one person; investigator moves in an inward spiral from boundary to center of scene, or outward spiral from center to boundary.
-perfect spirals are difficult, evidence can be missed
-inward spiral, move from area light in evidence to heavier
-eit
Wheel or Ray Search Pattern
Several people move from one boundary straight toward center of scene (inward) or from center straight to boundary (outward).
-areas between rays aren't searched, though.
Quadrant or Zone Search Pattern
divides scene into zones or quadrants
-team members assigned to each section
-sections can be subdivided into smaller sections for smaller teams to search thoroughly
-best for scenes covering large areas
-must include all probable points of entry/exit use
Locating physical evidence
investigators must rely on experience from past investigations to successfully recover relevant physical evidence
-homicide case, look for weapon or evidence as a result of contact between victim/assailant (hairs, fibers, blood)
-look for tool marks at po
Critical areas of the crime scene should be...
vacuumed, with the sweepings sent to the lab for analysis
-portable vacuum cleaner with special filter attachment
Things to be collected and sent to a forensic lab
1) victim's clothing
2) fingernail scrapings
3) head and pubic hairs
4) blood (for DNA typing)
5) vaginal, anal, and oral swabs (in sex-related crimes)
6) recovered bullets from the body
7) hand swabs from shooting victims (for gunshot residue analysis)
Mobile Crime laboratory
-carry necessary supplies to protect crime scene; photograph, collect, and package physical evidence, and perform latent print development.
-better name would be "crime-scene search vehicle
Handling evidence
-must handle and process phys evidence in a way to keep change from happening between time evidence is taken, and time it's received by lab.
-such as via contamination, evaporation, scratching/bending, careless or improper packaging
-latex gloves/ disposa
To take a bloodstain from a crime scene, one may...
...scrape the stain off the surface, transfer the stain to a moistened swab, or cut out the area of the object bearing the stain.
Packaging evidence
place each different item or similar items collected at diff locations in separate containers, to prevent damage through contact and cross-contamination
Packaging biological materials
-unbreakable plastic pill bottles for hair, glass, fibers
-manila envelopes, sealable plastic bags, metal pillboxes for trace evidence
-charred debris from suspicious fire must be sealed in airtight container to prevent evaporation of volatile pretroleum
Small amounts of trace evidence can be packaged in...
...a druggist fold.
-fold one end of a paper over by one-third, then fold the other end one-third over that, repeating process from other two sides. Afterwards, tuck outside two edges into each other to produce a closed container that keeps specimen from
When collecting biological materials...
...use only disposable tools
-don't store airtight, or moisture may accumulate and grow mold, destroying value of blood.
-instead use wrapping paper, manila envelopes, paper bags.
-must handle with minimum personal contact to avoid infections or contamina
DNA Evidence
-can be detected by saliva, sweat, or skin cells.
-sources include stamps, licked envelopes, gum, bedsheet.
-key concern is contamination
--preventable by face mask, disposable latex gloves, possibly coveralls
-must take all clothes from victim and suspec
Chain of Custody*
a list of all people who came into possession of an item of evidence
-adherence to stand procedures in recording location of evidence, marking for identification, and properly completing evidence submission forms for lab analysis help with court
--avoid q
A minimum chain-of-custody record would show...
...the collector's initials, location of the evidence, and date of collection.
-any transfer of individual, or to a lab, must be recorded in notes/etc.
-anyone who possesses the evidence must keep a written record of its acquisition and disposition
Standard/Reference Sample*
physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene evidence.
-few investigators seem aware of the importance of supplying this to the crime lab.
Buccal Swab*
a swab of the inner portion of the cheek;
-cheek cells are usually collected to determine the DNA profile of an individual.
Substrate Control*
Uncontaminated surface material close to an area where physical evidence has been deposited;
-this sample is to be used to ensure that the surface which a sample has been deposited doesn't interfere with lab tests
-ex: normally collected at arson scenes.
The mark of a skilled investigator is...
thorough collection and proper packaging of standard/reference specimens and substrate controls.
Submitting Evidence to the Lab
Personal delivery or mail shipment
-method determined by distance of lab and urgency of case.
-postal regulations restrict shipment of certain chemicals, live ammunition, explosives.
-most labs require an evidence submission form
-each item is to be packa
Ensuring Crime-Scene Safety
-increasing spread of AIDS and hepatitis B provides hazards.
-both normally spread through exchanged body fluids, intravenous drug needles and syringes, and transfusion of infected blood products.
-inoculation can easily prevent hep B infection in most pe
Guidelines to protect investigators at crime scenes with potentially infectious material (pg 45-46) 1-4
From the International Association for Identification Safety Committee
1) At scenes like a homicide, personnel wear doubled latex gloves and protective (Tyvek-type) shoecovers; liquid repellent coveralls in large contamination areas.
2) particle mask/resp
Guidelines to protect investigators at crime scenes with potentially infectious material (pg 45-46) 5-8
5) note taking done wearing uncontaminated gloves. Pens/markers disposed of before leaving scene.
6) immediately remove soiled/torn individual protective equipment.
-then personnel must disinfect/decontaminate potentially contaminated body areas using a r
Legal considerations at the crime scene
-material is often deemed as legally unusable as evidence b/c of "unreasonable" search and seizure of evidence
-any removal of evidence from a person/crime scene must be done with conformity to Fourth amendment.
Allowances for a warrantless search
1) emergency circumstances
2) need to prevent immediate loss or destruction of evidence
3) a search of person or property within immediate control of the person provided it is made incident to a lawful arrest
4) search made by consent of parties involved
Mincey v Arizona" case
-legality of a four-day search at a homicide scene.
-police officer pretended to buy drugs, then forced way into Mincey's apartment, and was killed.
-police found tons of evidence, and sent it to trial
-but b/c of the illegality of the search, the Supreme
Michigan v. Tyler
-business establishment leased by Loren Tyler was destroyed by fire; extinguished in early hours of the morning
-too hard to see, to conduct an investigation; building left unattended until 8 AM when inspection began. Items collected that day, 4 days, 7 d