The Provision of Forensic Services to the Criminal Justice System
Forensic scientists have a very important role in the criminal process: from initial crime scene investigation to forensic laboratory analysis to providing expert forensic statements and culminating in their appearance in court as an expert witness. Forensic scientists do not just perform forensic analyses and report on the results. As expert witnesses they are allowed to provide opinion as well factual evidence in criminal cases. Interpretation of certain factual evidence and opinions relating to it may vary between forensic experts; which is where forensic defence experts come in to the equation. Many will be extremely experienced and long serving forensic scientists who can use their experience and expertise to re-examine the forensic evidence and peer review any statements from the Crown's experts. Where appropriate, they can offer alternative forensic expert interpretation and opinion and appear in court as an expert witness for the defence.
Forensic science is divided into several disciplines and most forensic scientists who act as expert witnesses will usually specialise in one or two particular disciplines, which is what makes them 'experts' rather than just someone with a general knowledge of forensic science as a whole. These forensic disciplines include Forensic Biology and DNA, Forensic chemistry (which includes marks and traces), Forensic Drugs, Forensic Toxicology, Fingerprints, Firearms and ballistics and Road traffic accident investigation. In many serious criminal cases the trial may involve obtaining forensic evidence from forensic scientists in a whole range of forensic disciplines.
To get a better idea of the role of the forensic scientist let us consider a few case scenarios:
Example case - The crime scene of a violent assault/murder where the victim's body is still at the scene.
At a crime scene of this nature there may be contact trace exchange, such as blood, DNA, hairs, fibres etc. between the victim and their assailant. This will involve a forensic biologist and necessitate forensic DNA analysis as well as fibre analysis, blood pattern analysis and should also include the examination of the victim's and suspect's clothing. All of this forensic evidence can then be interpreted by an expert forensic biologist.
There may be blood stains, smears and splashes, all of which if interpreted correctly by an experienced expert forensic biologist can indicate a possible scenario of what took place at the crime scene before and after the victims death.
There may be fingerprints to be lifted and examined by a fingerprint expert and shoeprints to be photographed and compared by a forensic chemistry expert to shoes found on the person or at the home of a suspected assailant.
It may be that it was suspected that the murder occurred after an argument fuelled by drugs and/or alcohol. Blood samples would then be taken at post mortem and sent to the forensic laboratory for forensic analysis for drugs and alcohol by a forensic toxicologist. The results of these analyses would then be interpreted by a forensic toxicology expert.
In a case of this type there could be several expert witness statements: from a forensic biologist, a forensic chemist, a fingerprint expert and a forensic toxicologist. The content of these statements may or may not be pulled together by an overarching statement from the 'lead forensic scientist' in the case.
Example case - The crime scene of a large scale cannabis cultivation run by a serious organised crime group.
Drugs scenes of this nature are invariably 'forensicated' by police personnel (PCs and SOCOs - Scenes of Crime officers). Photographs are usually taken, cannabis plant samples are submitted to the forensic laboratory for forensic examination and forensic analysis and then usually the whole scene is dismantled and all the other cannabis plants are disposed of. This makes the job of a forensic drugs scientist quite problematic as they have to make their interpretation of the scene from photographs and the few sample cannabis plants submitted, with the rest of the forensic evidence having been destroyed.
The role of the forensic cannabis cultivation expert is to identify and analyse the cannabis plants submitted and, based on the photographs and police information about the crime scene to give opinions on the conditions under which the cannabis plants were grown and to estimate the potential yields of cannabis which could have been produced at the scene and ultimately sold. As the information available to the forensic drugs expert is limited, opinions of Crown and defence experts about potential yields can often vary and crucially depend on the levels of experience and expertise of the forensic experts involved. Cannabis cultivation on a large scale is usually a carefully controlled process as any deviation from optimum conditions could dramatically affect potential yields and the monetary value of a crop. It is important to assess plant yields properly as sentencing and asset seizure (under the proceeds of crime act) depend on crop value.
Established and experienced forensic drugs experts engaged by the defence may also be able to estimate crop values, based on their long-term knowledge of drugs markets and the different types of cannabis products sold in them. Original crop values are usually estimated by police 'experts'.
Forensic science is divided into several disciplines and most forensic scientists who act as expert witnesses will usually specialise in one or two particular disciplines, which is what makes them 'experts' rather than just someone with a general knowledge of forensic science as a whole. These forensic disciplines include Forensic Biology and DNA, Forensic chemistry (which includes marks and traces), Forensic Drugs, Forensic Toxicology, Fingerprints, Firearms and ballistics and Road traffic accident investigation. In many serious criminal cases the trial may involve obtaining forensic evidence from forensic scientists in a whole range of forensic disciplines.
To get a better idea of the role of the forensic scientist let us consider a few case scenarios:
Example case - The crime scene of a violent assault/murder where the victim's body is still at the scene.
At a crime scene of this nature there may be contact trace exchange, such as blood, DNA, hairs, fibres etc. between the victim and their assailant. This will involve a forensic biologist and necessitate forensic DNA analysis as well as fibre analysis, blood pattern analysis and should also include the examination of the victim's and suspect's clothing. All of this forensic evidence can then be interpreted by an expert forensic biologist.
There may be blood stains, smears and splashes, all of which if interpreted correctly by an experienced expert forensic biologist can indicate a possible scenario of what took place at the crime scene before and after the victims death.
There may be fingerprints to be lifted and examined by a fingerprint expert and shoeprints to be photographed and compared by a forensic chemistry expert to shoes found on the person or at the home of a suspected assailant.
It may be that it was suspected that the murder occurred after an argument fuelled by drugs and/or alcohol. Blood samples would then be taken at post mortem and sent to the forensic laboratory for forensic analysis for drugs and alcohol by a forensic toxicologist. The results of these analyses would then be interpreted by a forensic toxicology expert.
In a case of this type there could be several expert witness statements: from a forensic biologist, a forensic chemist, a fingerprint expert and a forensic toxicologist. The content of these statements may or may not be pulled together by an overarching statement from the 'lead forensic scientist' in the case.
Example case - The crime scene of a large scale cannabis cultivation run by a serious organised crime group.
Drugs scenes of this nature are invariably 'forensicated' by police personnel (PCs and SOCOs - Scenes of Crime officers). Photographs are usually taken, cannabis plant samples are submitted to the forensic laboratory for forensic examination and forensic analysis and then usually the whole scene is dismantled and all the other cannabis plants are disposed of. This makes the job of a forensic drugs scientist quite problematic as they have to make their interpretation of the scene from photographs and the few sample cannabis plants submitted, with the rest of the forensic evidence having been destroyed.
The role of the forensic cannabis cultivation expert is to identify and analyse the cannabis plants submitted and, based on the photographs and police information about the crime scene to give opinions on the conditions under which the cannabis plants were grown and to estimate the potential yields of cannabis which could have been produced at the scene and ultimately sold. As the information available to the forensic drugs expert is limited, opinions of Crown and defence experts about potential yields can often vary and crucially depend on the levels of experience and expertise of the forensic experts involved. Cannabis cultivation on a large scale is usually a carefully controlled process as any deviation from optimum conditions could dramatically affect potential yields and the monetary value of a crop. It is important to assess plant yields properly as sentencing and asset seizure (under the proceeds of crime act) depend on crop value.
Established and experienced forensic drugs experts engaged by the defence may also be able to estimate crop values, based on their long-term knowledge of drugs markets and the different types of cannabis products sold in them. Original crop values are usually estimated by police 'experts'.
Source...