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

I. OVERVIEW OF FORENSIC SCIENCE DNA EVIDENCE
The work of the forensic scientist: IBMS West of Scotland Branch Meeting
A well-attended IBMS West of Scotland branch meeting in early November
saw Marie Campbell from Strathclyde Police forensic science department
give a fascinating overview of the work of a forensic scientist.
Her first point was to explain the difference between a forensic scientist and a
forensic pathologist - the latter deals with autopsies while a forensic scientist
deals with the scene of crime, evidence investigation and DNA testing.
Forensic science divides into forensic chemistry and forensic biology. Forensic
chemistry deals with drug testing, marks and unique striations on tools used in
crimes such as burglary, footwear marks, fire scenes, firearms and shooting
incidents, forged documents and handwriting, threatening letters or money.
Drug testing is the perhaps the busiest role with thousands of cases processed
every year. Fire debris is sifted through to find small pieces of evidence that
would suggest a deliberate cause. The way a fire 'naturally' takes hold in a room
indicates whether it was started deliberately but evidence can still be hard to find
when it is covered by debris or a collapsed ceiling.
Physical chemistry looks at footwear comparison and gelatine lifting off a
suspect's shoes. Footwear comparison involves the electrostatic lifting of
footwear if a burglar has stood, for example, on a newspaper. The footprint can't
be seen but dust lifted off the paper to see the print on foil will show the unique
footwear marks that are made by an individual because of the way he or she
'treads' and wears the shoes.
Forensic chemistry also looks at paint comparisons - a trace of paint in a hit and
run accident can link back to a vehicle. Marie illustrated the point in a local case
where a kidnapper hit a tree before making his escape. Laboratory analysis of
the paint left on the tree was able to confirm manufacture of the car and the year
it was made allowing the police to quickly identify local suspects and find the
kidnapper.
Chemical etching is another technique employed to uncovered erased serial
marks. The plate can be dipped sulphuric acid to find out the original marks.
Firearms Discharge Residue analysis is another area of investigation. Residue
can be found on hands, clothing and in vehicles - part of the evidence used to
2