Commentary on: Pressman MR , Caudill DS . Alcohol‐Induced Blackout as a Criminal Defense or Mitigating Factor: An Evidence‐Based Review and Admissibility as Scientific Evidence. J Forensic Sci 2013;58(4):932–40.

Sir, Pressman and Caudill provided an excellent and detailed review about the questionable scientific nature of alcoholinduced blackout as a criminal defense (1). One other scientifically invalid aspect not specifically discussed in their study was the blood alcohol concentration (BAC) calculation by the defense expert in their example case. According to the example, the expert calculated that the defendant’s BAC after consuming three bottles of vodka was 0.350 g of alcohol in 100 mL of blood (g/100 mL). This type of calculation is also scientifically invalid as it is impossible to calculate an exact BAC from a drinking scenario, and a range of rates of elimination (such as between 0.010 and 0.030 g/100 mL/h) must be employed (2). In addition, the BAC calculations are typically based on Widmark’s pioneer work on 20 male and 10 female subjects who consumed a moderate dose of alcohol, bolus (within 5–15 min) on an empty stomach after an overnight fast (3,4). These conditions rarely occur in criminal cases, and in more realistic experiments of prolonged drinking and large amounts of alcohol consumed, the Widmark calculations have been found to overestimate the actual BAC by up to 50% (5). Thus, even the basis of the defense opinion that a high BAC occurred in the defendant (and caused an alcohol-induced blackout) was highly questionable scientifically.