Crime scene procedures and search principles

primary scene

where the crime occurred

secondary scene

other location where evidence can be found

organised crime

a group of individuals who plan and participate in illegal activities

unorganised crime

crime committed without involvement of organised group / not planned such as robbery, vandalism etc

securing the crime scene

Crime scene is secured and isolated

cordoned off using crime scene preservation tape - ensure area is large enough to preserve all areas of the scene

cordon may be adjusted at a later stage if necessary

prevent unauthorised personnel from having access to scene

a record is kept of any personnel entering and exiting scene including dates and time

crime scene search

if scenes of crime examiners SOCE cannot recognise trace evidence or cannot properly preserve it for lab exam

no amount of technical expertise can salvage the situation

objective is to retrieve maximum amount of evidence

achieved by a professional and methodical approach

objective of crime scene search?

to retrieve maximum amount of evidence

Crime scene preliminary survey

the searcher surveys entire scene to ascertain what types of evidence should be looked for

nature of the crime scnene offers the first clue to type of evidence that may be obtained

physical evidence - any object that can establish that a crime has been committed or can link a crime, victim or perpetrator

can range from large objects to microscopic traces

recording the scene

Crime scene recorded in its untouched state

items of physical evidence are photographed where they are found

dimensions of the crime scene are sketched having been measured

sketch indicates all items of relevance that were located

position of the body or indications of struggle are carefully noted

accurate detailed notes

must include a record of the time each physical item was discovered by whom and how it was packaged

video can be recorded with a narrative but must also be transcribed into a written document

searching for evidence

always important even if we have a suspect and motive

defence will always argue negligence in investigations

how to search crime scene?

depends on size and locale of crime scene

what to search for?

depends on circumstances of crime

need to collect possible carriers of trace evidence as well as more obvious objects

crime scene search methods

point to point

spiral search

zone method

strip method

grid search

point to point search method

movement following a chain of objects which are obvious evidence

spiral search method

carried out by a single person involves the searcher walking in a circular fashion from the outermost boundary towards the central point of the cordon off area

do not start in the centre as vital evidence may be destroyed while walking toward the central area

zone search method

the entire scene is divided into zones which are search individually

this is the most suitable when searching for a small object such as a bullet

strip method search

area is divided into strips about 1 metre wide

the searcher examines each strip separately until a thorough search has been conducted

usual method for an outdoor large area

grid search method

an advance on the strip method and used in large areas

searchers having completed the latter search are doubling back perpendicularly across the area being searched

more time consuming than strip method but is very methodical and thorough - searched from two different view points

each square is assigned a number or letter

searching indoors

walls and ceilings should also be examined and its best to work from the top down

remove floor boards as liquids such as blood and accelerants may easily run in between boards

critical evidence may be found in the least obvious places - blood behind radiators

if exit or entry path of criminal is identified, all authorised personnel entering the scene should use another entrance

searching outdoors 1

method used for searching outdoor are similar to that of indoors but nature of site will influence what amaterials will be collected

evidence such as fingerprints will be found less frequently

trace evidence can still be obtained through cans, bottles, weapons found close to the scene

all evidence recovered will be on the ground - could easily be overlooked or trampled

searching outdoors 2

if any doubt exists as to the value of an item, treat it as evidence until proven otherwise

ensure that each item or area where latent fingerprints or trace evidence may be present is throrughly examined

carefully protect any 2D or 3D impressions as they may be destroyed by weateher

searching outdoors 3

note all stains, spots and pools of liquid within the scene and treat them as potential evidence

note any odours present at the scene - presence of accelerants

SOCE should consult a member of the household in order to ascertain which items are foreign or could belong to an offender

retrieving evidence

packing material and labels should be available before commencing any search - new and free of all contamination

before taking possession of any item of evidence make a detailed note of its position and appearance

each item should be properly packed and labelled before the next item

retrieving evidence

avoid contamination such as breakage, evaporation, accidental scratching or bending

items with impression marks must be packaged to prevent movement during transport

blood, hairs, fibres must not be removed from garments

stains on large objects may be cut out or removed with a moistened swab

primary transfer of trace evidence

occurs through direct contact between items from different aspects of the case or between victim and suspect after the incident

secondary transfer of evidence

the same member of the police of SOCE handling items from different aspects of the case

when does contamination occur?

occurs when any trace evidence transfers to exhibits or to the scene after the crime was committed and prior to the forensic analysis

two sources of contamination of a crime scene

SOCE - any person at the scene or any person close to an exhibit may in advertently transfer his or her own DNA, hair or clothing fibres

An exhibit or person may be contaminated through contact with an unclean surface. Foreign DNA could transfer to the deceased from the mortuary table

Avoiding contamination 1

examiners handling exhibits should wear clean, disposable over garments, gloves and masks until all items are packed and sealed

never talk over an exposed item as its very easy to transfer DNA via droplets of saliva

examination surfaces such as tables or mortuary slabs should be thoroughly cleaned before use

avoiding contamination 2

items should be packed, sealed and labelled prior to removal from the scene

items should not be reopened prior to their examination by the forensic analysist

different police should deal with different sides of the case

person selected to take samples from suspects should not recently have handled the following materials - bulk drugs, explosices or firearms

samples of liquid accelerant should be packed and stored separately from samples of fire debris

information that must be on evidence collection bag

police district concerned

nature of occurrence or crime

name of the injured party

name of the accused/suspect

brief description of item

when and where the item was found

identifying number assigned by officer in charge of the case

name of person who found this particular item

date

evidence containers for collection of trace evidence

manila envelopes

screw cap glass vials

sealable plastic bags

why should airtight containers not be used for bloodstained materials?

they may grow mould

why seal charred debris in air tight containers?

to prevent the evaporation of volatile petroleum residue

Glassine evidence envelopes

used for collecting hairs, fibres, glass shards and paint shards

eliminate static electricity and are breathable, transparent and have a flap to seal the evidence

clear plastic tubing with rubber end capes and styrene inner cushion

used for sharp objects

lined, all metal evidence cans with air tight lid

collection of arson scene evidence with possible accelerant contamination

standard/reference samples with example

comparison of evidence

removal of paint from suspects vehicle to compare with that of paint on the body of a hit and run victim

control sample example

unstained areas of clothing analysed at same time as blood stained to check that material is not affecting lab results

Submission of evidence to laboratory

evidence submitted together with a form detailing case history

facilities logical analyses of evidence as well as search for trace evidence

all items of evidence are listed and numbered

form specifies tests/analysis to be carried out on each item

maintaining chain of custody 1

record maintained of all those who handled, transported or examined evidence

continuity of possession must be established whenever evidence is presented in court

any person involved in the handling of the exhibit at any stage will be required as a potential witness

each witness should be in a position to give evidence as to what they done with the item along with dates etc

maintaining chain of custody 2

when the relevant examinations have been completed, the items are handed over to exhibits officer who will prepare a chart recording all the movement of each item

as each item is handed over it should be accompanied by a signature and a receipt

best practice in the handling of exhibits dictates that as few persons as possible handle the exhibit

Crime scene safety

biological specimens of unknown origin may be present

caution and protection are required

Hep B vaccine given to CS investigators

Double latex gloves,

4 ways of processing a crime scene without a search warrant

to prevent the loss of evidence

to prevent the loss of life / if immediate threat to life is identified

if an arrest has been made

if consent is given by the landlord