The Role of the Forensic Scientist in the New Millennium With the Example of Fire Debris Analysis, by Eric Stauffer

As far as criminal investigation dates back, the most important role of the forensic scientist has always been known as to help the courts to prove the existence of a crime, identify its victim(s) and perpetrator(s), and reconstruct its modus operandi. This role will not undergo any major changes in the new millennium.

However, some other important responsibilities or liabilities, totally implicit in the role of the forensic scientist, belong to him/her and need to be reminded. They consist in preventing forensic sciences from becoming dubious sciences by making sure that the duty of the forensic scientist goes smoothly from the crime scene to the trial and ensuring the reliability of the forensic examination. These responsibilities have always been incumbent upon the forensic scientist.

Nevertheless, with the tremendous development of the technology and methods applied to forensic sciences these last few decades, it has become increasingly difficult to satisfy these responsibilities. Moreover, some recent events involving the FBI and/or other law enforcement agencies, showed in a very obvious way that these requirements were not always met. This fact contributes strongly to the degradation of the opinion that people have of forensic sciences and particularly of the scientists that work in this field. If people lose confidence in forensic sciences, they will not contribute anymore to the quest for the truth, but will rather be the new questionable topics in trials. Hence, instead of being an auxiliary of the courts as it should be, forensic sciences will be the new defendants in the trial.

Therefore, it is possible to define a new role to the forensic scientist: the need of reminding and ensuring the proper application of his/her responsibilities. In order to realize that, it is necessary to improve forensic scientists' awareness of their responsibilities, which imply three important levels of the process of forensic examination: the chain of custody, the quality-assurance control, and the interpretation of the evidence. This concept will be illustrated with the example of fire debris analysis.

First of all, chain of custody as the first step of evidence collection, needs to be perfectly fulfilled and respected. Not only is there a constant increase in the number of cases and of samples collected at the crime scene, but there is also a greater number of people working on one set of evidence or one case than a few decades ago. Hence, the chain of custody can be nowadays a real challenge that forensic scientists must overcome successfully. The smallest lack of professionalism might break the chain of custody and thus, lead to the non-admission of the evidence into court. In the worst case scenario, it can lead to a contamination of the evidence or a loss of a pertinent element. Without an irreproachable chain of custody, it is not possible to maintain the integrity of the sample analyzed and thus, ensure the significance of the results obtained. No matter the sophisticated analytical tool or state-of-the-art method used for this examination, the results will not be representative of the evidence as it was found at the crime scene, unless the chain of custody is maintained.

Also important is the fact that the chain of custody does not stop at the door of the laboratory once the evidence is received from the crime scene. It is also an internal step and since at least a couple of scientists will work with the evidence, one must be careful to respect this chain within the laboratory.

In fire debris analysis, chain of custody begins with the sampling of the fire debris at the fire scene. While at one time a given forensic investigator was processing the fire scene, determining the cause and the origin of the fire, sampling the possible evidences, and analyzing them in the lab, some considerable changes have occurred. The levels of specialization required in the different fields of forensic sciences make a crime scene almost overcrowded by the forensic personnel. This means that the evidence will be carried in multiple hands; for example: the fire investigator, the person in charge of evidence collection, the fire debris analyst, and the supervisor. Furthermore, every single step in the examination can bring new contamination and the number of steps have greatly increased these last years with the development of new analysis processes.

These conditions make the chain of custody more and more difficult to respect and thus, require more awareness from the people dealing with evidence.

Secondly, the forensic scientist will be more aware of the quality control of his/her work. This century ended with some famous cases affecting the whole forensic community where the quality of the work did not even reach an acceptable level. By quality, one must understand validity of the procedure used, and the way the procedure is applied. With the advances of technology and analysis methods, a tremendous diversity of new scientific methods came to the forensic scientist. Naturally, he/she has more chances to choose the wrong one, or a less efficient one than a few decades ago.

The extraction procedures are a good example of these comments in the field of fire debris analysis. In the late 50’s, the fire debris analyst did not have to hesitate very long before choosing one of the only techniques available at this time for ignitable liquid residues (ILR) recovery. Steam distillation was well accepted and efficient for this time. Nowadays, the use of steam distillation for general processing of fire debris will be almost considered as a lack of knowledge in the field. Furthermore, the choice of the technique could be a longer step than before since one must choose between several techniques (passive headspace concentration, active headspace, solvent distillation, solvent extraction, etc.), each of them presenting advantages and drawbacks. Not to mention the fact that for each of them, multiple parameters can be changed (adsorbent and heating process, desorption process and solvent used, etc.).

The availability of procedures and methods must be controlled, and this can only be done by professionals in the specific field of the application of the procedure or method. This shows how necessary is the validation of the procedure by peer-review and forensic associations. The way the procedure is applied can be controlled by two people. The first person is the forensic scientist him/herself, while the second will be his/her supervisor. Again, the famous cases of this century’s end showed as an example that even within an important forensic laboratory, the supervision and peer-review was not considered as important as it should be.

Therefore, it is important for the forensic scientist to ensure not only that valid procedures and methods are used, but also that they are applied properly. This will strongly contribute to an improvement of the quality of the work done by crime laboratories and thus, will greatly improve the image of the forensic sciences.

Then, the forensic scientist not only has to perform analyses, but also has to understand and interpret the results obtained. Analyses are more and more sophisticated and constantly offer a decrease in the limit of detection. Forensic sciences analyze yet smaller and more complicated samples than decades ago. This is great because a smaller amount of sample is needed and a greater range of samples is available. On the other hand, this makes it more challenging to interpret the results. For example, the use of GC-MS or even GC-MS/MS allows now the detection of very weak traces of gasoline, which were not detectable 10 or 20 years ago. A recent case of a house fire, suspected as arson, revealed traces of gasoline on floor samples. The presence of gasoline strongly supported the hypothesis of the arson. However, further analyses showed that the gasoline contained lead and thus, was very likely there for a very long time and was not related to the fire. Another example is the interference of pyrolysis products released by burning substrates in the ignitable liquid residues (ILR) identification. At the beginning of fire debris analysis, this problem was not known and identification of ILR were not supposed to have interfering products that can be naturally present in a fire.

These two examples show how important it is for the forensic scientist to question him/herself about the value of the results. Placing the results in a context and elucidating what their worth and what they mean is not an easy task and should be rigorously trained in the future.

In conclusion, a certain laxness has been observed the last years in regards to the work done in forensic laboratories. This is likely partially due to the excess of new techniques that became available to the forensic scientists. Lack of time to properly manage the set up of these techniques in the lab, overflowing caseload of the laboratory, and constant increasing of the knowledge required to perform the analysis are also strong contributing factors. This led to a lack of standard methods and of systematic quality assurance/quality control. This is an important fact and it should not be set aside. It is now time, with the new millennium, for the forensic scientists and the forensic community to realize these mistakes and correct them. Several measures are already in place like ASCLD[1] or ABC[2] certifications or the different TWG or SWG[3]. Furthermore, concerning the interpretation of the evidences, publications have been more and more frequent these last years and several authors are leading investigations on this subject.

But without the complete willingness of the forensic scientist handling and working with the evidence, all these measures will not have the effect expected. He/she should never forget the first purpose of the forensic sciences, serving and helping the courts, and this cannot be done by performing junk science.


[1]  American Society of Crime Laboratory Directors, which offers accreditation for laboratories

[2]  American Board of Criminalistics, which offers certifications for scientists with different specialty examinations

[3]  Technical and Scientific Working Groups are available for different fields of forensic sciences