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Ask Penny

Please post your questions for this week in the comments section. Penny will select the most liked/interesting questions and publish her response to these on this step by Wednesday of Week 6.

Firstly, thank you very much for all your excellent questions and comments again this week, I hope you are enjoying the final week of the course, bringing together all of the scientific evidence we have looked at as the case has unfolded.

In case anyone hasn’t yet found the answers to the ‘Ask Penny’ questions from Week 3, you can access these on the ‘Ask Penny’ article in Section 3.15.

One thing I wanted to comment on was how great it was to see that you’re all keen to continue working together; many of the questions asked this week and in previous weeks have already been addressed and answered by other participants and that’s really great to see you all engaging in the content.

This week, your questions were mostly about the drug evidence, so I’m going to focus on this in my answers. Hopefully any remaining questions you have will be cleared up in the final big reveal of the verdict on Friday…

The questions relating to the analysis of illicit substances covered a few different areas, and there were questions and comments from Anne Martin, Gary Lee and Michael Moitzheim and about the use of presumptive and confirmatory tests, drug profiling and clandestine laboratories.

On the topic of presumptive testing for drugs, for all of these tests, there are a variety of substances that can cause false positive results on the tests, which means that the results of these tests cannot be used to definitely conclude that a substance is present. As such, a presumptive test cannot be reported formally, and a forensic scientist would not testify in court about the results of such a test. False positive results on presumptive tests for drugs have been reported, as a result of cross-reaction with drugs that are not illegal, including some prescription/pharmaceutical drugs, such as aspirin. In addition, some everyday substances give false positive results on these tests, for example Pritt stick glue gives a false positive on a test for cocaine, and nutmeg and thyme give false positive results on a cannabis test. The issue with this potential for false positive results means that presumptive tests cannot be relied upon, and more detailed confirmatory analysis needs to be carried out before a forensic scientist can conclude that a substance is present. The only time that a presumptive test result would be presented in court would be if the accused individual has admitted to possession of the drug tested for, and then this test would be admissible. In all other cases, a confirmatory test would be required, and this would usually be a GC-MS test. This relates to the question about TLC and GC-MS and why both tests are done. Whatever presumptive test is carried out is useful for indicating what substance may be present, and this also helps the drugs analyst to determine exactly how the confirmatory test will be done, so the TLC result can give an indication of what should be done as a follow up. The presumptive test is cheap, quick and simple and prevents the lab from having to use up more resources testing for different drug types using the confirmatory technique. However, if the lab had a trace drugs case, where there was only a very small amount of the drug, then they might well skip the presumptive test step and go straight to a confirmatory test.

Kim Waghorn asked about the length of time to go to trial and unfortunately there is no specific answer to this, if an individual pleads guilty to an offence their sentencing hearing can take place quickly but otherwise, a trial may not take place for months depending on the complexity of the crime, location and court scheduling.

In relation to drug profiling, in the UK, forensic service providers all have their own drug testing labs and these will all have the capability to do drug profiling. However, drug profiling is not actually done very often as it is very costly, and usually the key issue is just to identify an unknown substance as being a specific controlled drug (using presumptive/confirmatory testing). Drug profiling would involve more detailed chemical analysis to determine the components present in the substance in question and to estimate the amount of each component (e.g. the drug, cutting agents, impurities). Many street samples contain cutting agents to bulk up the drug for sale, for example, a sample of heroin might also contain diamorphine, paracetamol, and caffeine, and potentially also things like mannitol (a sugar) or anti-fungals. Identifying these different components of a sample can be useful in linking different batches of drugs together, and also in linking drugs to a production site/lab.

Tsvetanka Palovska asked about the production of new drugs and how law enforcement deal with this. A major issue in forensic drugs analysis in recent years has been the analysis of ‘new psychoactive substances’, previously known as ‘legal highs’. These terms refer to chemicals that used to be legal, but produced similar effects to illegal drugs such as cannabis, amphetamines and cocaine. These were produced with the aim of avoiding the laws controlling the use of illicit substances, which in the UK is the Misuse of Drugs Act (1971). For example, synthetic cannabinoids are a group of chemical compounds that mimic the effects of cannabis. This is because they are synthesised to have structures that allow them to bind to the body’s cannabinoid receptors. The drugs originated in the late 1980s to early 1990s, by chemists who understood how these receptors were bound by the active ingredient of the cannabis plant, ∆9-tetrahydrocannabinol (∆9-THC), which produces the ‘high’ associated with this drug. Synthetic cannabinoids were therefore produced to imitate this effect, by binding the cannabinoid receptors in a similar way. The use of these substances increased hugely in the last decade or so, particularly in Europe, as the chemicals involved were not controlled or regulated by law. In addition to this, very often as forensic drug analysts became familiar with the chemical structure and nature of one legal high, and therefore were able to test for it, the drug producers would adjust the chemical structure of the substances slightly so that the drug’s effect remained the same but the chemical was undetectable in standard drug screening tests. This, in combination with a rise in incidents of poisoning and the number of fatalities, led to an increasing need to regulate these drugs.

Controlling these substances has been very difficult around the world, as no countries had laws to regulate them. However, in the UK, this changed in 2016, when the Psychoactive Substances Act came into force. This law is a blanket ban on the production, distribution, sale and supply of these substances, and these activities are now punishable by up to seven years in prison. Legal highs are added into the list of banned substances as they are discovered, after forensic drug analysts have determined the chemical structure of the substance, and the health risk posed by the compounds has been assessed. However, our pharmacological understanding of these substances is still very limited, and this has slowed progress in identifying new psychoactive substances. New substitutes for legal highs evolve at such a rapid pace that is difficult for the authorities to keep up with, and the drug producers are generally always ahead of the law. If you would like to read more about legal highs, this BBC article gives some more information about them , and this article discusses the introduction of the Psychoactive Substances Act in 2016.

With regards to determining the origin laboratory of drugs seized, the majority of drug testing done in forensic laboratories is not done to identify the origin lab, so linking to a source lab is relatively rare, and the forensic analysis part of drugs investigation is often completed very quickly. However, if the chemical structures produced in different labs are different then they can be differentiated using chemical analysis and so this can be a very powerful method. Another analysis that the police/prosecution may request that the forensic laboratory carry out is to test the purity of a drug. This would depend on what type of case it is—if the police are only charging someone with possession of a drug then the purity would not be important and the forensic analysis would simply involve identifying the drug. However, if someone was being charged with supplying a drug, then the purity would be tested in order to estimate the street value of the sample seized, and this could influence a sentence or fine later on.

In terms of central coordinated databases of drugs, forensic providers maintain their own databases and regularly make this information available to police, documenting the different types and quantities of drugs found in a given time period. There are also some projects collecting data to monitor seizures of different types of drugs when recovered in relatively large quantities, and these can be used for intelligence purposes.

Gwen Boult correctly pointed out that there was no toxicology report on Mrs Ward reported in the case. Toxicological analysis can produce very important forensic evidence, and this is one major area of expertise that forensic scientists can specialise in. Unfortunately, we simply did not have time to cover every type of forensic evidence in six weeks, and so it was not possible to include toxicology in the course at this time.

All that remains now is to say that I hope you enjoy the rest of the material in Week 6. The video revealing what really happened will be made available at the end of the week, and we are asking you to vote for whether you think Mr Ward is guilty or not guilty. We really hope you will take the time to vote, and we would love to see lots of responses. I would also encourage you to vote according to your analysis of the evidence, and not on your gut feeling. This week we have been looking at a logical system for bringing together evidence, analysing it and thinking carefully about what it means from a scientific point of view. You should therefore focus on the science, work through it all logically and base your decision solely on what the evidence tells you. I really hope you have enjoyed the course, it has been a real pleasure interacting with you and reading all your comments and questions. I have really enjoyed seeing how interested you have all been in the case, and how much discussion you have had about it each week. Thank you very much for joining us for the Introduction to Forensic Science MOOC, and don’t forget to cast your vote before 16:00 GMT this Friday!

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This article is from the free online course:

Introduction to Forensic Science

University of Strathclyde