Guest post by Dr. Michael Robertson – Independent Forensic Consulting
Dr. Robertson is a forensic toxicologist at Independent Forensic Consulting and a specialist consultant to a range of medico-legal organisations. Dr. Robertson graduated with a Doctor of Philosophy in Forensic Medicine from Monash University with a background in pharmacology, toxicology and analytical chemistry. Dr. Robertson is an expert in drug and alcohol-related matters and has assigned, supervised, performed and certified hundreds of toxicological analyses and has testified as an Expert Witness in most courts within Australia for prosecution, defence and plaintiff lawyers. He holds membership of The Australian and New Zealand Forensic Science Society (ANZFSS); The International Association of Forensic Toxicologists (TIAFT); the Society of Forensic Toxicologists (SOFT) and The Forensic and Clinical Toxicology Association of Australia (FACTA). He has been a member of the SOFT Drugs and Driving Committee and the SOFT Drug Facilitated Sexual Assault Committee and also serves as an invited reviewer for the international journal, Forensic Science International.
In the past quarter, IFC have reviewed a number of reports in which experts have concluded or implied that simply the presence of a drug infers impairment or that a drug has caused or contributed to an event when it was simply administered by medical professionals after the event.
Drugs and Impairment
- The presence of a drug in blood is only consistent with use
- Some information about dose and time of use may be inferred however in the absence of either unusually high levels in the blood or corroborating evidence of impairment i.e. observations that are consistent with the likely affect of the drug, impairment cannot be assumed due in part to issues associated with tolerance; dose; time of dose etc. etc.
- That is, the presence of a drug or drugs in the blood does not imply impairment, simply the possibility of impairment
- Drugs are often administered by paramedics at the scene of an incident or enroute to hospital. They may also be administered by hospital staff once they have arrived at hospital
- Common medications administered by paramedics or hospital staff includes: morphine and fentanyl for pain management; Maxolon (metaclopramide) for nausea; midazolam for anxiety, among others
- Whilst many of these drugs can impair and may show clinical signs consistent with impairment i.e. drowsiness, poor balance, confusions and slurred speech etc. they obviously played no role in the causation of the incident if administered post-incident
- The administration of drugs should be well documented in the Ambulance and / or Hospital records
- Q: Is there a BAC at which time an individual will be visible intoxicated?
A: Due to many variables including an individual’s tolerance to alcohol and learned behaviour i.e. ability to walk and talk whist intoxicated, there is no BAC that when reached all individuals will show signs of visibly intoxicated. That said studies have shown that at or about 0.15% it is more likely than not that one or more visible signs of intoxication will be evident e.g. poor balance, confusion, slurred speech etc.
- Q: Does Speed (methylamphetamine) in the oral fluid imply my client was impaired?
A: No. The presence only means that the drug has been used in the 12 or so hours prior to sample collection. Impairment would have to be established via other corroborating evidence i.e. driving behaviour, visual observation of the individual
- Q: Do drug levels change after death?
A: By and large, the answer is yes. Depending on when the sample was collected relative to death and from what part of the body blood was drawn (central or peripheral), drug concentrations may go up or down after death (in general, more likely up).
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