With EU support, the 11 members
of the Nite-Crime network, comprising forensic science institutes, chemical
analysis, and other research organisations, are developing sophisticated
chemical analysis (mass spectrometry) techniques. These will enable the
identification - with very high certainty - of a range of non-organic
materials. The techniques will be disseminated to forensic and other research
institutes to enable the build-up of validated databases. Precise identification
of the original source of substances such as glass, bullets and paint
is invaluable in forensic studies.
witness: glass particles for analysis, which are found on suspects
and at crime scenes, are very small compared to a paper clip.
© Bundeskriminalamt, Wiesbaden, Germany.
Determining the exact origin of materials found
at the scene of a crime can result in the vital evidence needed
to implicate a suspect. This is especially true as criminals have
become more sophisticated and now take care not to leave any materials
or traces of their presence at the scene of a crime which can link
them through DNA testing. There are many more traditional and long-standing
methods that are used to identify traces of inorganic materials,
such as refractive index, which can establish that two glass samples
originate from the same glass source. However, there is often room
for uncertainty with these methods, which may be unacceptable in
a court of law.
Other problems complicate the issue still further:
- often there is only a very small quantity
of sample available, which means there may be enough for just
one analysis, or the number of repeat or corroboratory tests that
can be made is very limited.
- the financial resources available to
the police for research purposes are increasingly limited, restricting
the extent to which sophisticated analyses are used.
- Institute of Food Research, Norwich,
United Kingdom (co-ordinator);
- Austrian Research Centres, Seibersdorf,
- Bundeskriminalamt, Wiesbaden, Germany;
- Forensic Science Service, Birmingham,
- Kriminal Technisches Zentrum, Vienna,
- Netherlands Forensic Institute, Rijswijk,
- Curtin University of Technology, Perth,
- Eidgenössische Technische Hochschule
- FBI Laboratory, Quantico VA, USA;
- International Atomic Energy Agency,
- US Customs Service, Springfield,
The mass spectrometer
is a specialised weighing machine. It uses the difference in mass-to-charge
ratio of ionised atoms or molecules to separate them from each other.
These ions must first be created, then separated and measured. Developments
in mass spectrometry now offer a range of techniques for determining
the trace-element composition or isotopic ratios of inorganic materials.
The key advance is the combination of laser ablation - to create
the ions - with various separation methods such as quadrupole, time-of-flight,
sector or multi-collector ICP-MS (inductively coupled plasma-mass
spectrometry). Parallel developments in the technology use ultra-violet
or excimer lasers to obtain lower wavelengths with a much higher
accuracy than was previously possible.
"Most analytical labs are already using
quadrupole ICP methods," explains the Nite-Crime co-ordinator
Jurian Hoogewerff of the UK's Institute
of Food Research, "but laser systems are expensive and
the laser-ICP combination would only be available at a regional
level." Using laser ablation is a very attractive option for
forensic investigators because the amount of sample required for
testing is very very small and, afterwards, the sample remains almost
unaffected and intact.
Laser ablation ICP-MS analyses a wide range
of elements in a sample, and can determine less than one part per
billion of some elements. It is now possible to distinguish between,
for example, two pieces of glass from two genuinely different glass
sources. This is because, although both might have some physical
properties in common, such as refractive index, they are quite different
as the glass fragments were made with the same type of raw materials
but from different geological sources.
The principle of laser ablation is that a laser beam hits a sample
within a closed area, through which a stream of inert gas is passed
- usually a mixture of argon and helium. Particles from the sample
mix with the gas to form an aerosol and, in this way, the mixture
is transported to the mass spectrometer where it is ionised and
"Quadrupole systems are the most commonly
used," according to Hoogewerff, "while time-of-flight
systems are extremely fast and can be very effective for transient
isotopic signals." The multi-collector systems offer extremely
precise measurements of the natural isotope ratio; however, both
systems are new and very costly. The exact choice of which method
to use for a particular problem will depend on a number of factors,
including the difficulty and importance to the case of the substance's
identification, the cost and availability of the equipment, and
the availability of the highly skilled staff necessary to operate
to crime scenes
In a murder case
where the police suspect that a body may have been moved from the
scene of the crime to the burial place, they will need forensic
assistance. An examination of the mineral debris on the body or
clothes can reveal the unique signature of its chemical constituents.
"Comparing the mineral breakdown of the fragments from the
two sites can show conclusively whether the body has been in either
or both places," explains John Watling of Curtin
University, Perth, Australia. "Similar analysis of mineral
deposits in car tyre tracks can be related to places where the car
has been." The new technique is a real boost to the work of
forensic scientists as it can give an unequivocal answer using extremely
Microscopic samples of lead or other metal
particles from bullets (down to 0.03mm) can be identified and even
pieced together from the fragments left in a victim's body. Then
their chemical identity is determined to find or disprove a match
with bullets from the weapons of those suspected of the crime.
And to fraudulent
Stefan Becker of
the German Forensic
Science Institute of the Bundeskriminalamt Wiesbaden, Germany
recounts one example of a non-personal crime which was elucidated
by the new technique. The Institute was approached by a major German
pharmaceutical company which suspected that a batch of its immune
human blood plasma was not German-made but, in fact, had been produced
in China. The quality of this serum was so high that no difference
could be detected from the authentic German plasma. Only by analysing
the trace element composition of its glass container could the true
origin be ascertained as Chinese-produced plasma.
One of the main aims
of Nite-Crime is to develop standard procedures. These validated
methods and techniques can then be used to build up databases of
the composition of those inorganic materials commonly found at crime
scenes - glass, bullets and gunshot residues, car paint and others.
"All substances used around the house," says Hoogewerff,
"are based on raw materials from some sort of geological source
- once we understand the trace element and isotope signatures of
these materials they can be traced through the whole production
Because the techniques are so new, work is still
needed to make them strictly comparable. Decisions are required
on the optimum conditions for laser ablation, which must be standardised
before reference identifications of materials can be recorded. For
this reason, the Nite-Crime network will concentrate during its
first year on setting these standards; later it will develop protocols
for the materials most commonly implicated in crime scenes.
The network is planning
to hold workshops, linked either to international forensic conferences,
or at the laboratories of network members. Aimed at forensic scientists,
the workshops will train participants in the use of the new techniques
to identify relevant suspect material. All the members of the network
believe that in time the new techniques will become better known
and applied by more skilled operators. Competition will eventually
bring the prices of the test equipment down.
Work is already under way in Australia to build
a mobile spectrometer for use at a crime scene, significantly cutting
both police and forensic officers' time. The new mass spectroscopy
method will be to inorganic analysis what DNA testing has been to
organic and human material - the key to identification with a high
level of certainty, once it becomes more widely available.
A thematic network has been set up under the
Growth Programme's measurement
and testing generic activity to assist in the fight against
fraud and crime.
The project is developing analysis techniques capable of identifying
the source of minute fragments of inert materials. It will help
to provide evidence to link an individual to a crime scene.
- Natural Isotopes and Trace Elements in Criminalistics and Environmental
Forensics (project no GTC-2000-28029).