– Originally published in The Expert Witness magazine in the Spring of 2016. Download the original PDF.
The Forensic Science Service (FSS) was the largest employer of gunshot residue (GSR) experts in England and Wales with an impressive array of instrumentation required for round the clock analysis of the samples taken from suspects of gun crime. Since its closure in 2012 the GSR criminal casework load was split between three main private forensic providers depending on their success or failure at tendering for the work being offered by the police forces in England and Wales. Less than half of the number of GSR experts from the FSS now work for these providers and the majority of the remainder left the profession. Scotland, Northern Ireland and Ireland have their own publicly funded forensic science providers. All of the laboratories must be accredited to the International Quality Standard ISO 17025:20051.
The examination of exhibits for the presence of GSR is generally undertaken at the laboratories. Some police forces may in-source this step in the forensic chain. The private forensic providers may also be commissioned to carry out defence work. Clearly however, this will only be for cases where they have not undertaken the work at the request of the police. In this instance, an alternate forensic provider may be commissioned or one of the independent forensic consultancies. One such consultancy is Forensic Firearms Consultancy who are regularly commissioned by solicitors, government organisations, law enforcement agencies and private individuals, across the globe, for both prosecution and defence work.
Overseas the analysis and reporting of GSR is undertaken by a mixture of government funded and private laboratories. There can be considerable differences in the way in which not only the GSR is examined for but also in its analysis and subsequently the manner in which the findings are presented in Court. It would be fair to say that the analysis for GSR, and ultimately the interpretation placed on the findings, is not the same no matter who does it…
When a gun is fired thousands of microscopic particles, called gunshot residue, are produced by the ammunition. They are emitted from the end of the muzzle of the gun and from any gaps or openings in the gun’s action and can be deposited on the firer, any persons or surfaces sufficiently close to the firer, and the gun itself. The recovery and identification of GSR particles can help address questions such as, ‘has the suspect recently fired a gun?’ That the particles originate from a firearm is rarely contested. Of far more interest to the court is how these particles came to be on a suspect’s clothing or hands. Because of its potential evidential significance in putting somebody at the scene of a shooting GSR is one of the most heavily scrutinised types of trace evidence in criminal investigations.
In the early 1970’s work began independently at the Metropolitan Police Service Forensic Laboratory in London and at the Aerospace Corporation in California on a new method of identifying individual particles of GSR using the scanning electron microscope equipped with an x-ray analyser, this equipment is known as SEM-EDX. Importantly, this work established that discrete particles composed of lead, barium and antimony appeared to occur only in percussion primer residue. There was no known source other than firearms, hence the technique became the first conclusive method for identifying GSR. This particle analysis method is still employed today.
In any population of GSR there will be a variation of the proportions and combinations of the chemical elements. Particles containing all 3 elements i.e. lead, barium and antimony were previously considered unique to the discharge of a firearm, however they have been subsequently observed elsewhere e.g. firework particles or car brake linings. Firework particles are usually produced with a profusion of other elements alerting an experienced scientist that they were not observing GSR. The appearance of particles from brake linings lack the features of particles produced at high temperature and therefore are not typical of GSR. Particles are therefore now widely referred to as being characteristic of originating from a firearm. Particles without all 3-components are referred to as indicative or consistent with a firearms origin.
Over the past 20 years or so the original acceptance criteria for the chemical components constituting a particle of GSR have been refined and widened. As a general rule, there are three main compositions of GSR particles commonly seen in casework and two that are seen more rarely. The differing compositions are used to distinguish between different Types of residue.
Indicative particles, containing one or two elemental components, are very rarely reported in the UK as they can also be found in materials commonly occurring in the environment however they are reported by a number of overseas laboratories.
The largest single factor that must be considered when interpreting GSR findings is the possibility of contamination. What is a contamination risk? This is defined, in forensic science terms, as the danger of the undetected transfer of GSR onto an item or sample after an incident has occurred. In general, small amounts of GSR particles are anticipated on samples taken from gun crime suspects so the opportunities for cross-contamination must be kept to a minimum and the risk must be assessed within the overall context of the case.
At a crime scene, as with any evidence type, appropriate protective clothing must be worn by anyone entering the scene. Clothing and samples from suspects’ skin and hair surfaces need to be recovered as soon as possible after the incident. It is also critical that the investigator does not handle any guns or spent cartridge cases and then come into contact with a suspect or other item that is to be examined for GSR. Separate individuals should be involved in the collection of evidence that may be highly contaminated with GSR and that which may only contain low levels.
At incidents involving firearms it is common practice for armed police officers to attend to secure the safety of the general public. In the most severe incidents this can mean incapacitating a suspect to prevent them from discharging a firearm that may injure themselves or others. The officers will also be involved in searching suspects thought to be in possession of a firearm and addresses where firearms may be located. Firearms officers are very likely to have GSR on their hands and clothing and this may be transferred through physical contact to a suspect. All details of the arrests of suspects involving firearms officers need to be considered when interpreting the GSR findings in a case.
FFC Ltd. is regularly instructed to review the GSR findings in firearms cases reported in the United Kingdom and overseas. As previously mentioned some overseas laboratories report indicative GSR particles, so called ‘one or two-component particles’. This is not a terminology that was used by the FSS. One such case involving ‘one and two-component particles’ was the attempted murder of Lo’Torean Durrant in Bermuda.
On the evening of 19th March 2013 four shots were fired at Mr Durrant as he got out of a taxi, a bullet passed through his back and into the taxi door. There were no eye witnesses. Police received information that two males were seen running nearby before getting into a vehicle. The vehicle was traced to an address and armed police officers attended. They found Blaine Simmons at the address, the address being the home of a friend, just as his mother arrived to pick him up and take him home. The officers were suspicious and handcuffed Mr Simmons before searching him. One of the officers removed a mobile phone from his pocket and handled it before it was placed into an exhibit bag recovered from the armed police vehicle.
The samples were sent to a private laboratory in the United States. A single particle of characteristic GSR was found on the mobile phone and a number of ‘one and two-component particles’ on Mr Simmons’ clothing, a motorcycle visor, and inside the vehicle found parked at the address. The majority were actually ‘one-component particles’. No characteristic GSR particles were found on Mr Simmons’ clothing that had been recovered five hours after the shooting. The single characteristic GSR particle and the ‘one and two-component particles’ were reported by an expert from the private laboratory in a factual report. The report did not mention the armed police officer involvement and handling of the mobile phone. A number of caveats were included which stated that GSR can be deposited by circumstances such as discharging a firearm, being in the proximity of a discharging firearm or coming into contact with a surface/object that has GSR on it. It was also stated that ‘one and two-component particles’ are found in GSR but may also originate from other sources.
During the trial in January 2014 at the Supreme Court in Bermuda prosecution sought to rule out any other source of the particles, in other words non-firearm sources, and to say that they were part of the same population as the single GSR particle found on the mobile phone. The particles had in fact been found on different items and surfaces recovered and sampled respectively at different locations and times to each other. The expert for the prosecution also stated that the morphology of the particles supported a firearms source in that they were spherical suggestive of originating from a hot process such as the discharge of a gun. This was speculation not supported by any documentary evidence provided with the case papers.
Importantly, it would not be expected that only ‘one and two-component’ particles would be found in the absence of characteristic GSR if they had originated from a firearm. It also needs to be considered that there are many environmental sources of ‘one and two-component particles’. FFC Ltd’s expert opinion was that the absence of GSR on Mr Simmons clothing, taken approximately 5 hours after the shooting incident, supported the view that whilst wearing the clothes he had not discharged a gun on the day in question. Single particles are the smallest possible finding and the particle on the mobile phone could have transferred from the armed police officers during the arrest or have been picked up unknowingly from the environment. Prosecution counsel put significant weight on the single GSR particle and ‘one and two-component particles’. A leap was made that the one and two-component particles were in fact GSR and that the particles were all from the same population.
After 9 hours deliberation the jury were unable to reach a verdict.
A re-trial was held almost a year to the day from the original trial. Prior to this FFC Ltd had conducted a very small survey in Bermuda taking 10 samples in total from seating and tables in the police social club, the Supreme court, the external surfaces of a police vehicle, and the waiting area in a police station. In total over sixty ‘one-component particles’, a single ‘two-component’ particle and a single characteristic GSR particle were found on the samples. The very small sample set suggests more particles would be found if a larger survey were to be conducted.
New evidence also emerged from the examination notes made at the time of the sampling of the mobile phone for the presence of any GSR. They highlighted that routine laboratory good practice had not been followed and as such there was a risk that the mobile phone had been contaminated during the examination.
Further details came out during the retrial regarding the practices and procedures of armed police officers in Bermuda and that there was a significant risk that the officers involved in the arrest of Mr Simmons could have contaminated the mobile phone.
FFC Ltd was of the opinion that the single characteristic GSR particle could have been picked up unknowingly from the environment, during Mr Simmons arrest or when the phone was sampled in the laboratory. It would be unsafe to conclude that the particle originated from an event other than one of those mentioned. In addition there was much discussion surrounding the one and two-component particles and all of the possible non-firearms sources of such particles. Following deliberation the jury found Mr Simmons not guilty.
This case serves to highlight that the analysis and more specifically the sampling and reporting of GSR is not undertaken in the same manner in different parts of the world. Such differences have so far only been discovered in some overseas cases reviewed by FFC Ltd. Reporting an unqualified finding of the presence of gunshot residue or not fully interpreting the findings can ultimately mislead the court. The court cannot appreciate the significance of possible contamination, for example, if it is not mentioned in a scientists report or oral testimony and the case may go ahead with the GSR findings unchallenged.
FFC Ltd scientists using their wealth of experience shall continue to diligently and expertly conduct unbiased reviews of the findings in the most serious of crimes, that is, crimes involving the use of firearms to ensure as far as possible that there is not a miscarriage of justice.
Angela Shaw
© The Forensic Firearms Consultancy Ltd 2016
