Investigating CSI – Background material Table of Contents I ...

DNA information. DNA testing can also be done on weapons - knifes collect skin
cells that can be profiled.
Sifting through scenes of crime for possible sources of evidence requires lateral
thinking and nothing can be discarded in case it develops significance later in a
police investigation. DNA testing now uses the quicker method of profile numbers
rather than 'barcodes'.
In sexual offences acid phosphate tests are used to identify semen. However, the
department also investigates the damage of underwear to determine whether the
damage is recent or self-inflicted. The ends of fibres can tell whether the
underwear is torn, cut or just very old. This type of investigation is obviously
important in rape cases.
Analysis of hairs and clothes fibres is another way of gathering evidence
although the success of DNA has meant that hair analysis is now rarely used.
Fibres can provide excellent proof of recent contact and can be used to back up
DNA evidence. Lateral thinking is needed in looking for samples - for example
how someone would have escaped from a crime and thus possibly left samples
while climbing a wall.
Forensic biologists also attend scenes of crime which can cover very large areas
- especially if streets have to be closed down. Forensic biologist can find
themselves in difficult working conditions - freezing cold fields in the middle of the
night or derelict buildings. Marie pointed out that TV programmes on forensic
examinations where sharp suited detectives wandered through the crime scene
instantly deciphering clues were far removed from reality. Scenes of crime were
now overseen by managers who ensure that the sites are secure to preserve
evidnece. Forensic scientists dress in all over white suits to avoid not only
contaminating evidence but also the evidence contaminating workers.
The National DNA Database was established in 1995 and holds DNA profiles
from mouth swabs (Criminal Justice samples - CJ)) of convicted criminals and
records of outstanding crimes. The database is run by the Forensic Science
Service in Birmingham although there are also local facilities at Dundee. The
database currently holds around two million CJ samples and 160,000 crime
scene profiles. Obviously the use of the database to solve crime can only
succeed if a suspect has committed a previous crime but since 1995 a large
amount of violent crime has been solved by running crime scene profiles against
CJ samples - including 1,000 murders and 1,800 rapes. Cases from the past
have been solved as the same person commits new crimes or new CJs are
logged on the database.
The lecture was followed by a question and answer session that included a
number of points including the necessary qualifications to enter a career as a
forensic scientist, recruitment and retention and quality audits.
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