Woody Will Smith, 33, is due for trial accused of murdering Amanda Hornsby-Smith, 28, in Kentucky.
His lawyer Shannon Sexton will argue Smith had so much caffeine in the days leading up to the killing that it rendered him temporarily insane – unable even to form the intent of committing a crime.
A caffeine defence is unusual but has succeeded at least once before, in a case involving a man cleared in 2009 of charges of running down and injuring two people with a car in Washington state.
Dr Roland Griffiths, a professor of behavioural biology at Johns Hopkins University, has noted in an unrelated study that there is a diagnosis for “caffeine intoxication,” which includes nervousness, excitement, insomnia and possibly rambling speech.
Prosecutors, meanwhile, said their own expert may testify there was no evidence Smith had consumed diet pills or energy drinks as he claimed before his wife died.
Prosecutor Michelle Snodgrass said Smith tested negative for amphetamine-type substances shortly after the killing.
Police say Smith used an extension cable to strangle his wife in May last year, then used it to bind her feet together.
Smith told psychologist Dr Robert Noelker he remembers taking his children to school that morning but little else.
“The next several hours of Mr Smith’s life were described to me as if he were in a daze,” Noelker wrote in a report.
Reports and case records say during that time he was drinking five or six soft drinks and energy drinks a day, along with taking diet pills; it all added up to more than 400 milligrams of caffeine a day.
The Diagnostic and Statistical Manual of Mental Disorders – published by the American Psychiatric Association showing standard criteria for the classification of mental disorders – defines overdose as more than 300mg, or about three cups of coffee.