26 terms

Crime scene search methods

point to point
Movement following a chain of objectives which are obvious evidence
spiral search
carried out by a single person involves the searcher walking in a circular fashion from the outer point of the crime scene towards the central point DO NOT START IN CENTRE AS EVIDENCE MAY BE DESTROYED
zone method
entire scene is divided into zones that are searched individually best for searching for a small object
strip method
area is divided into strips about 1 metre wide. the searcher examines each strip separately. best for outdoor area
grid searching
advance on the strip method searchers complete the strip method and double back across the area being searched
searching indoors
walls and ceilings should be examined beat to work from top downwards critical evidence may be found in the least obvious places
searching outdoors
similar to indoors, fingerprints found less frequently, almost all evidence will be on the ground.pay attention to fragile evidence as it may be destroyed. protect 2D or 3D impressions footprints. note any odours.
retrieving evidence
packaging must be new, before taking any item make a note of its position and appearance, each item should be properly packed and labelled
avoid contamination
avoid breakage, evaporation, accidental scratching or bending
blood, hair, fibres, soil
do not remove from clothes weapons etc before sending to lab
stains on large objects may be cut out or removed using a swab
sources of contamination
contamination occurs when trace evidence transfers to or from the scene after crime and before forensic analysis
crime scene examiner
may transfer there own DNA hair or fibres to crime scene or evidence
primary transfer
direct contact between items from different aspects of the case or between victim and suspect after incident
secondary transfer
same person handling items from different aspects of the case
avoiding contamination
wear clean disposable over garments, gloves and masks, never talk over evidence, clean all examination surfaces, items packed sealed and labelled before removal from the crime scene and not reopened before examination different police should deal with different sides of the case, victims and suspects not be transported in the same car.
labelling items
each item should have a clear lable with this information police district concerned, nature of occurrence or crime, name of injured party, name of accused suspect, where and when item was found, identifying number, name of person who found the item, date
evidence containers
envelopes, screw cap glass vials, saleable plastic bags, air tight containers should not be used for bloodstained items as mould may grow paper bag is used instead, charred items of fire should be sealed in air tight containers to stop evaporation of petroleum residues
glassine evidence envelops
used for collecting hairs, fibres, glass, paint eliminates static electricity
clear plastic tubing with rubber cap
for sharp objects
all metal evidence cans
collection of arson evidence
comparison of evidence to known standard
removal of pint from suspects vehicle to compare with paint on body of hit and run victim
control samples
unstained areas of clothing compared at the same time as blood stained to check material is not affecting lab results
submission of evidence to laboratory
evidence submitted together with a form derailing case history, all items are listed and numbered, specifies tests to be carried out
maintaining chain of custody
record kept of all who handled evidence
continuity of possession
to be established whenever evidence is presented in court