Blackouts – Understanding the Impact of High BAC

sleeping off a bingeFollowing on from my previous blog about alcohol induced blackouts, lets review a case report by D. Wells (WOA61707) as it illustrates the importance of blackouts in criminal cases.

A 27 year old woman (weighing 110 pounds) who was a rare, social drinker of alcohol was drinking at a bar with her girlfriend.  A man from an adjoining table joined them.  After socializing for some time, the woman went to the ladies room and, after returning, finished the drink that she had left on the table.  Shortly afterwards, she began to feel dizzy, confused and nauseous.  She awoke in her bed some nine hours later, partially undressed, and had no memory of how she got home.  An expensive ring was missing from her hand.

The case was investigated by the police as a possible Drug Facilitated Sexual Assault (DFSA) with robbery.  She was examined approximately 12 hours after her last drink.  There were no features of recent injury or sexual intercourse.  Her breath smelled of alcohol and horizontal gaze nystagmus was present.  A breath test was conducted and revealed a blood alcohol concentration level of 0.120 g/100mL.

The police contacted her girlfriend as part of their investigation.  The girlfriend stated that the man had left the table at the same time as the woman went to the toilet and advised she had not seen the man since.  She said that the woman had become more and more intoxicated and had fallen asleep.  In addition, the woman had vomited on a number of occasions.  She drove the woman home and partially undressed her and placed her in bed.  The expensive ring was later found at the woman’s home beside the toilet.

A retrograde extrapolation, or back calculation, of the woman’s blood alcohol concentration was calculated to some 12 hours earlier, using elimination rates found in women of between 0.013 and 0.028 g/100mL/h (WOA10306).  This retrograde extrapolation indicated a peak BAC of between 0.273 and 0.456 g/100mL.  Since she was a rare, social drinker it would be expected that her rate of alcohol elimination would be in the lower range (WOA10301) and, therefore, at the lower range of the estimated BAC.  She also may have obtained a lower blood alcohol concentration as she vomited any alcohol that had remained in the stomach.  A good reflex which helps prevent potential alcohol poisoning.

This reported case applies most of the principles or characteristics that were discussed in my previous blog (i.e. a BAC > 0.230g/100mL, rapid drinking, total amnesia, etc).  It also illustrates the potential serious consequences that can occur with blackouts.  If it wasn’t for good police/forensic investigation, an innocent man may have been charged with DFSA and robbery or at least brought into the police station for questioning.  There was no malice on the part of the woman, she had just wanted to find out what had happened to her that night (“connect the dots”) and perhaps was influenced by media sensationalism about DFSA.

Another study on blackouts concluded that:

“Becoming aware that a blackout had occurred was often accompanied by a sense of dread or apprehension.  Many subjects later learned that they had gotten into fights, had sexual experiences, or had been arrested during a blackout.  Factors that would increase the slope and peak of a subject’s BAC curve, like gulping drinks or drinking on an empty stomach, seemed to precipitate blackouts” (WOA60304).


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