Pre-Trial Procedures The Criminal Investigation
Expectations CL2.01 explain the processes of police investigation CL2.02 explain pre-trial procedures, including processing evidence
The Crime Scene Police have the right to cordon off the crime scene to make sure no evidence is lost or tampered with. Police can refuse entry to a crime scene. If the incident involves a death, the coroner has jurisdiction over the area.
The Crime Scene Continued The area will be photographed and searched for items such as hair or fibre samples, blood, forced entry, physical struggle, fingerprints, footprints, or weapons, or other evidence. ▫This is called forensic evidence. Police will also question witnesses about their knowledge of the crime or the persons involved.
The Crime Scene Continued There are strict procedures on the seizure, handling, and storage of evidence: 1.no evidence is left unattended; 2.the case officer must secure evidence in the police property locker; 3.transferring evidence is the responsibility of the case officer; 4.no evidence can be removed from property locker without appropriate authority and signature. This is to maintain the chain of custody of the evidence.
Processing Evidence: Fingerprints Forensic scientists analyze the information collected. Fingerprints are compared with those on file at the RCMP central repository in Ottawa. The patterns of ridges on our finger pads are unique: no two individuals—even identical twins—have fingerprints that are exactly alike.
Injuries such as burns or scrapes will not change the ridge structure: when new skin grows in, the same pattern will come back. Dactyloscopy is the practice of using fingerprints to identify someone.
Mistakes can be made in fingerprint identification as usually only a portion of a print is available and can be distorted and hard to read, especially in a messy crime scene situation. It is extremely important that specialists are able to properly dust and lift fingerprints at a crime scene to be able to classify and match them to those in the database.
Are we able to classify our own fingerprints in class? YES!
Classifying Fingerprints All fingerprints can be identified as one of three types: Arches, Loops, Whorls 1.Arches: forming ridges that run from one side of the print to the other and curve up the middle
2.Loops: showing stronger curves than arches with ends that start on one side of the finger, loop around and end up in the same place
3.Whorls: forming complete ovals, often in a spiral pattern around a central point.
Your turn! Directions: Print your name on the lined side of one of your cue cards – set it aside Take two pieces of scotch tape and tape them together to create a ‘thicker’ piece of tape ▫(sorry guys, the dollar store only had skinny tape) ▫Set the tape aside (on the end of your desk) Rub the second cue card roughly with your pencil Press your index finger on the pencil-lead dust Place the sticky side of a piece of transparent tape on the dusted finger Take the tape with the fingerprint and tape it on your first cue card on the blank side – not the side with your name on it Label the fingerprint to identify which finger you have printed (i.e., Index or I) and classify your print using the fingerprint handout
Dusting for Fingerprints It is extremely important that specialists are able to properly dust and lift fingerprints at a crime scene to be able to classify and match them to those in the database. Dusting is a method that is used to lift prints from hard surfaces Chemicals are needed to lift prints off smooth surfaces
Directions: Dusting for fingerprints 1. Press your index finger in the play-doe. 2. Press your index finger on the glass 3. Coat the fingerprints with a dusting of baby powder. 4. Lightly press the powder with the brush – but don’t brush off the powder! 5. Bang the glass on the desk to get the excess powder off the glass. 6. Place the sticky side of the tape on the dusted fingerprint. 7. Lift off the tape and place it on the black construction paper. 8. Print your name on the back side of the print.