Techniques of Crime Scene Investigation - Final Exam

what are elimination prints

a set of prints obtained by consent

who are elimination prints taken from

- witness

- employees

- family members

- other individuals

why are elimination prints necessary

- good practice for all since examination

- assists with the prompt and accurate examination of all crime scene impressions found

crime scene impression

unknown source

elimination prints

known source

I.C.E

- Incriminate (puts the suspect at the scene or in possession of that item)

- Corroborate (the witness stuart of victims explanation of occurrences

- Eliminate (the victim and other people not involved)

where do we take elimination prints from?

1. stolen vehicle - how else drives this vehicle or is frequently in it?

2. B and E - who else lives with you or is over often/shortly before the mite of offence

3. threading letters/fraud - who handled the items prior to police showing up

4. robbery - who were the employees working? were there other people in the store at the time of the offence?

what happens to elimination prints?

- elimination prints are compared ONLY to the case in question

- they are NOT kept on AFIS and compared to further outstanding cases

- a request must be put through in order to have the pints destroyed

obtaining elimination prints

- powder tips of fingers lightly with black powder

- flat lay all 4 fingers and thumb onto sticky side of shipping label (right and left hand)

- label placed onto clear acetate sheet (case #, date, your name, persons name, left or right hand)

criminal prints

- identification of criminal act (including mugshot, height, weight, etc)

- prints SHALL be provided once charge with an offence - regardless if convicted or not

- prints SHALL be taken each time an individual is charged (no choice, you have to give prints)

- finger print service number

- if you’ve been arrested but not held in custody - you will be released on a release document with a fingerprint date

- reasonable force

- federal charges require fingerprints

arrested - fingerprints

1. rolled ink - C-216 RCMP form

2. rolled ink - glass and paper method

3. live scan

how does a digital camera work?

similar to film - shutter opens and allows light to strike the image sensor

image sensor

charged couple device CCD

- contains light sensitive pixels that measure the light energy striking each pixel

- a colour filter (Bayer Filter) sits on top which allows certain pixels to only measure certain colours of light

bayer filter

- RBG primary/additive colours

- each pixel only reads one colour

- weigh out the light to determine the colour

image sensors (CCD or CMOS)

- charged couple device/complementary metal oxide semiconductor

1. CCD - horizontal and vertical row of charge capacitors

2. CMOS - each pixel has its one ABC attached, information gets converted immediately

analog to digital converter

- as light hits the pixels, an electrical charge is created and a measure in the change of voltage is recorded at each pixel site

- the data collected in each pixel gets converted into a digital signal

circuit board

- carries the data from the image sensory (CCD or CMOS) and stores it to the memory card

display screen

- review photos

SWGIT recommendations

- scientific working groups on imagining technology

- goal is to ensure that successful introduction of forensic images in a court of law

- cell phone images, special effects, filters are not considered acceptable means of introducing photography in court

SWGIT recommendations - section 1.4

digital imaging is an accepted practice in forensic science, law enforcement, and the courts

SWGIT recommendations - section 2.1 equipment

- image capturing devices should be capable of rendering an accurate representation, different application will dictate different standards of accuracy