Tammi Lynn McMullen was convicted of two counts of first-degree homicide by vehicle and driving under the influence of drugs after her car struck a stationary trailer, killing two people. Blood testing found methamphetamine, morphine, and phentermine, and an expert testified that their combined effects likely impaired her driving. The jury also heard evidence of McMullen’s 1997 methamphetamine-possession conviction. The Georgia Court of Appeals held that the evidence was sufficient for the jury to find drug-related impairment even though witnesses saw no obvious external signs. But it reversed the convictions because the decade-old drug-possession offense had no meaningful similarity or logical connection to whether McMullen was impaired while driving on the charged occasion; admitting it improperly invited a propensity inference. The court held that voluntary consent permitted admission of the blood evidence without implied-consent warnings under the amended statute. It also held that a forensic expert could testify about testing performed by others when the expert independently analyzed the resulting data, rather than acting as a conduit for a non-testifying analyst. Because the evidentiary error was trial error rather than insufficiency, the State could retry McMullen without violating double jeopardy. The judgment was reversed.