The Case of the Burnt Bowls: or what you need to know to be successful in forensics. (Feature/Chronique).
Jamie (ISI): Hi Rick, how are you doing and what's up?
Rick (forensic engineer): An odd fire down near St. Marys, flash kitchen fire with some stuff on the stove. I'll send Sharom back with some stuff, hell fill you in.
Jamie: Sounds good, I'll be in this afternoon and we can likely get right on it.
Later that afternoon. Sharom enters laboratory with the evidence.
Jamie: Hi, Sharom. Rick called, what do you have?
Sharom (forensic engineer): Well, these bowls were on the stove and that appears to be the origin of the flash fire, although it's hard to tell. The place wasn't too badly damaged but these bowls are pretty burned up inside. I guess we need to know what the guy was doing on the stove before the insurance can be paid. Any ideas?
Jamie: It looks like the guy was cooking something. It's pretty black. I suspect there isn't much chance of finding residual liquid accelerant, although the residue itself might tell us something. We'll take a look at it in the lab and I'll give Rick a call tomorrow with our ideas.
This was the start of an interesting case back in 1993. The names (except the author's) and places have been changed as criminal proceedings may still be active. Amongst other scientific and consulting services at ISI, we have been supporting the forensic engineering, industrial, legal, and insurance industries with forensic analysis and problem solving for 10 years now and, in that time, have participated in many routine and non-routine cases. This is one of the less routine problems that required a solution.
On with the case!
The evidence was a pair of standard stainless steel kitchen mixing bowls with burn marks and a small amount of black, burnt greenish oily residue in the smaller bowl. We inspected the bowls and residue and our senior chemist performed a few quick spot tests and solubility checks. We postulated that the residue contained an oily component (ie. solvent soluble) and was likely a plant-based product but could be petroleum-based. It looked like the bowls were used like a double boiler, with water in the larger one and the original oily substance in the smaller one. This type of rig would be used for an extraction or to heat something in a controlled fashion to 100[degrees]C.
I called Rick back and we discussed the details. It sounded like the guy whose house burned had a pot farm in the basement, with lights and a few dozen marijuana plants. He was known in the area. We agreed we would test the residue for materials consistent with cannabis extraction.
The odour had made us suspicious before. We checked the literature and determined illicit cannabis extractions are generally done with a light organic solvent -- hexanes, light petroleum distillates, or alcohol. This was consistent with what we had observed and also with the flash fire, often caused by the ignition of vaporized light solvents. Our experience with botanical extractions told us that a dichloromethane extraction and GC/MS analysis of the residue would show most of the common plant oils such as phytol and the literature indicated that the compounds diagnostic with cannabis (tetrahydrocannabinol and cannabicyclol) should also be apparent.
The residue was removed from the bowl (see above) and a portion extracted with dichloromethane, dried, and run on the GC/MS (30 m non-polar column) under open scan conditions. The resulting chromatogram and computer spectral match are shown on the following page. As can be seen, the largest peak in the extract was phytol (1550 scans) which is characteristic of any 'green' plant extract (ie. leaves, stems, flowers but not necessarily fruit or roots). The second largest peak (1990 scans) was identified by the GC-MS computer with a 99.0% match as delta 9-tetrahydrocannabinol, the main psychoactive ingredient of cannabis. There was not much doubt about the identity of the material. The compound cannabicyclol was also detected at 1840 scans.
From this we concluded the bowls were being used as a water bath rig to either extract the active ingredients of cannabis, namely hash oil, or to remove the solvent after extraction. Although the residue indicated the guy was doing a pretty good job, through some misadventure the fumes from the solvent must have ignited causing the flash fire in the kitchen. This was reported to the forensic engineer investigating the case.
Interestingly, we followed up later and found out that the house insurance claim was refused, not because of the illegal substance, but because extracting hash oil is not considered a 'normal' use of a home stove, so the resulting damage from the fire was not covered. Several months later the regional police force contacted us for a copy of our report to assist in an ongoing criminal investigation.
What We Need to Know
The 'burnt bowls' case is one of over a hundred forensic investigations we have participated in over the past 10 years. Most of these, as people in the business will know, are relatively standard investigations looking for liquid accelerants indicating arson in fire residue. These are done using a standard set of ASTM methods. The non-arson jobs like the example above, however, are much more unusual.
Several years ago we adopted the ISO 9001 quality system to help us in providing systematic and legally defensible work for our clients. During this exercise we sorted out some of the key aspects of successfully completing these 'investigative' jobs. On the surface, they seem merely interesting problems requiring a bit of deductive reasoning and, perhaps, luck. But completing them successfully, and in a legally defensible fashion, requires the melding of the ISO concepts of good project management with the formalities of the scientific method.
Some of these key concepts are:
* Contract Verification: It is very important to clearly understand what questions need to be answered. Exchange information and ideas with the site people, often forensic engineers, and also, if applicable, with the legal or insurance people responsible for the overall outcome. Confirm what you are planning to do and what question you will be answering with your work. The ISO-9001 system forces the formalization of this process.
* Notes and Records: The need to keep accurate, dated and traceable notes and records cannot be overemphasized. Sample security and traceability as well as dated and traceable lab and field books are a bare minimum. Take photographs and document all observations. Record all meetings and have standard procedures for as much of the technical work as possible. Again, the ISO system formalizes this, requiring the files to be organized, complete, traceable, and auditable.
* Tests and Experiments: Central to the process are tests and experiments that actually prove the solution to the problem. Some of the more routine work, for example arson tests, follow well established procedures and require only good chemists and suitable equipment. The more complicated jobs however, require innovative and creative experiments to answer questions. To successfully answer these questions without ambiguity, the experiments must be well designed. Karl Popper, a philosopher and the father of the scientific method, said the hypothesis -- that is, the expected answer from the experiment -- must be disprovable or the experimental result is not conclusive. In the day-to-day world showing this 'disprovability' usually takes the form of controls. In the simple arson test, the chemist also must test a blank to be sure the assay is not giving a false positive and a spike to make sure the assay is not giving a false negative. In more complex investigations it can take some careful consideration to make s ure the experiment is valid and defensible. In some cases, it is impossible, making that particular experimental approach useless.
* Conclusions: At the end of our investigation we give our answer, and it must be objective. This answer is based on the information we have been provided and whatever we could find out from our field investigations and laboratory tests. At this stage it must be clear what we do know and what we do not know. It is easy to stray into an overconfident position. In our example of the bowls we may be inclined to say the solvent from the bowl extraction caused a flash fire. In fact we only know that components of cannabis were in the bowl and the fire had destroyed any hope of seeing an accelerant. Our work is therefore not conclusive, but only supportive of that fire scenario.
It is also important to note that reports for this type of work are not usually extensive so it is very important that the entire body of work supporting the report can be directly traced from the report and can be audited. This may be necessary in the case of a court case or dispute. In our experience records in an 'ISO-organized' fashion are not disputed.
In the end, the successful completion of forensic work demands a combination of creativity, objectivity, painstaking attention to detail, and openness to scrutiny. A firm understanding of scientific methods helps keep the creativity objective, good solid field and laboratory practices keep the details recorded, and an ISO 9001 or similar system assures the work will stand up to audit and scrutiny. And -- best of all -- it's fun.
James Ford, M.Sc., is a principal of Investigative Science Incorporated (ISI), a scientific consulting, field service and laboratory company in Burlington, ON. Mr. Ford has been working on forensic projects for over 15 years. ISI is now celebrating its 10th year supporting forensic investigations.
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|Publication:||Canadian Chemical News|
|Date:||Oct 1, 2001|
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