Spiked Drink Expert Witness Case Study 5

Independent forensic expert evidence in a spiked drink case

Bericon Forensics was instructed to provide independent forensic expert witness evidence in a drink-driving case involving an alleged spiked drink.

The defendant was charged with driving with excess alcohol. He stated that he had knowingly consumed only two pints of Stella Artois lager.

A witness suggested that the defendant had also unknowingly consumed approximately 100 ml of vodka after alcohol had been added to one of his drinks.

The forensic expert’s instructions

A forensic alcohol expert witness was asked to review the available information and carry out alcohol calculations to assess:

• whether the defendant’s account was scientifically plausible;
• whether the stated consumption of lager and vodka could explain the evidential alcohol reading;
• what the defendant’s alcohol concentration was likely to have been at the time of driving;
• the likely contribution made by the alleged spiked drink; and
• whether the defendant would have been below the legal limit without the additional alcohol.

Independent forensic alcohol calculations

The forensic expert carried out forward and back calculations using the supplied drinking history, timings and evidential alcohol result.

The forward calculation indicated that, without the contribution of the vodka allegedly added to the drink, the defendant’s blood alcohol concentration would have been below the statutory limit at the time of driving.

Further back calculations showed that the stated consumption of two pints of lager and approximately 100 ml of vodka was capable of accounting for the later alcohol reading.

The calculations therefore supported the possibility that the additional alcohol had made a material contribution to the evidential result.

Expert witness conclusion

The forensic alcohol expert witness concluded that the defendant’s account was scientifically plausible.

The calculations indicated that the defendant may have been below the legal alcohol limit at the time of driving had he consumed only the two pints of lager he knowingly drank.

The alleged spiked drink provided a credible explanation for the additional alcohol reflected in the later evidential reading.

Case outcome

The magistrates found the defendant not guilty.

This case demonstrates how an independent forensic expert witness can use alcohol calculations to assess whether an alleged spiked drink is consistent with the measured alcohol result and the defendant’s likely concentration at the time of driving.

Instruct a forensic alcohol expert witness

Bericon Forensics provides access to experienced forensic experts and expert witnesses for cases involving:

• alleged spiked or laced drinks;
• drink-driving allegations;
• blood, breath and urine alcohol results;
• forward alcohol calculations;
• back calculations and alcohol elimination;
• post-driving alcohol consumption;
• hip-flask and special-reasons cases;
• review of prosecution alcohol evidence; and
• independent expert witness reports.

Our forensic alcohol experts can assess the drinking history, calculate likely alcohol concentrations and explain their conclusions clearly for solicitors, counsel and the court.

Contact Bericon Forensics to discuss the instruction of a forensic alcohol expert witness.