Overdoses from prescription drugs have sometimes led to civil or criminal charges against prescribing physicians, but even toxicologists have problems distinguishing between overdose deaths and fatalities from other causes, Time reported June 16.
The result is that the courts, not heath officials, are often left to determine drug users' cause of death.
Complicating factors include use of alcohol or other drugs in combination of prescription medications and underlying health conditions. Even Steven Karch, a cardiac pathologist considered the leading expert on overdose deaths, says that current medical technology can't determine which drug actually caused a patient to die.
Drug tolerance among patients varies and grows over time, meaning that an effective painkilling dose for one patient could be deadly for another. Karch said it is therefore impossible to determine a standardized “lethal dose.”
“Postmortem redistribution” — a shift in detectable drug levels that takes place after death — also can confound diagnosis of overdose deaths.
Juries, however, are often swayed by courtroom testimony that makes diagnosis of overdose deaths seem far more certain than it is. “It's a giant miscarriage of justice,” said Karch.