Adrienne Martin had cocaine and the prescription painkiller oxycodone in her system, but it was impossible to determine how she got the drugs, St. Louis County prosecutor Bob McCulloch said. An autopsy identified an oxycodone overdose as Martin's cause of death, but McCulloch said she had taken lethal levels of both drugs.
"It was clearly an accidental overdose," McCulloch said. "There's no evidence to support any kind of finding that she may have been forced to do anything other than taking the drugs voluntarily."
Busch's attorney, Art Margulis, said the decision not to file charges "was the only logical and reasonable conclusion. There really never has been a basis for criminal action, but I hope the extensive investigation will clear the air and bring closure."
McCulloch offered an updated account of Martin's final minutes: Busch woke up at 12:45 p.m. Dec. 19 and tried to wake her up about 15 minutes later. An aide in his home also tried to wake Martin, and then the two called police, who arrived at 1:12 p.m. Paramedics arrived soon after, and Martin was pronounced dead at 1:26 p.m.
Despite previous reports that Busch was slow to call for help, "there is no time gap," the prosecutor said.
Neither Martin nor Busch had a prescription for oxycodone, McCulloch said. Martin took that five or six hours before she died and cocaine about an hour before.
"The levels on each were significant enough that either one could have caused her death alone," McCulloch said.
A telephone number for Adrienne Martin's mother, Christine Trampler, was disconnected and there was no new listing. A message requesting comment from her ex-husband, Dr. Kevin Martin, was not immediately returned. Kevin Martin has been caring for the couple's 8-year-old son since his ex-wife died.
McCulloch said Busch was largely uncooperative in the investigation, talking to police only the day that Martin died. "The investigation as to where the drugs came from is a dead end," he said.
Margulis said Busch was singled out because he is well-known and he told his client not to speak to prosecutors.
McCulloch said the autopsy showed no evidence of a rare heart condition that Kevin Martin had said he diagnosed in his ex-wife, although more tests would be needed to confirm that. The tests weren't done because it was clear oxycodone was the cause of death, the prosecutor said.
Friends had said Martin was strongly opposed to illegal drugs, but investigators released a report Thursday that said Martin had a nasal septum perforation, sometimes a sign of cocaine use.
Busch told the St. Louis Post-Dispatch last month that Martin was taking Trazodone, an antidepressant sometimes used to treat insomnia, but McCulloch said there were no traces of that drug in her system.
Oxycodone, commonly known by its brand name, OxyContin, is used to relieve moderate to severe pain, according to the National Institutes of Health. The Drug Enforcement Administration says abuse of the drug has increased markedly in recent years.
Busch, 46, was the last chief executive officer of St. Louis-based Anheuser-Busch Cos. Inc. before the company was sold to Belgian brewer InBev in 2008 - two years after he was named CEO. Busch remains a member of InBev's board of directors but had otherwise disappeared from public view since the merger.
Busch told the Post-Dispatch that he spiraled into depression after the sale, which he opposed. But he called Martin's death the saddest time of his life.
Busch, whose 2006 marriage to Kathryn Thatcher lasted less than three years, has had other troubles.
When he was attending the University of Arizona in 1983, he left a bar near Tucson, Ariz., with a 22-year-old woman. His black Corvette crashed, and the woman died. Busch was found hours later at his home. He had suffered a fractured skull and claimed he had amnesia. After a seven-month investigation, authorities declined to press charges, citing a lack of evidence.
Two years later, Busch was acquitted by a jury in St. Louis on assault charges resulting from a police chase that ended with an officer shooting out a tire on his Mercedes-Benz.
AP reporters Jim Suhr in St. Louis and Christopher Leonard in Clayton, Mo., contributed to this report.