PINELLAS PARK — Two years ago, a man in a 1973 Rolls-Royce blew through a red light and killed an 81-year-old man driving with his wife to Walmart.

A Pinellas Park officer suspected Tracy Garon, the driver of the Rolls-Royce, was drunk. The officer led the 59-year-old to a curb and resumed investigating at the crash scene. Left to himself, Garon walked into a Circle K and bought a 24-ounce Miller Lite.

The officer saw Garon leave the convenience store with the beer to his lips and told him to stop drinking. Garon kept swigging. The officer grabbed the beer and placed it on the sidewalk.

"At this point, I had suspicion to believe this act was an attempt to defeat a DUI investigation," an officer wrote of the Dec. 9, 2012, crash.

Stories of how to beat a DUI test abound. And expert opinions vary on how much people could torpedo a DUI case by drinking after a crash and before a breath or blood test is administered.

"It could certainly muddy the waters," said Reta Newman, director of the Pinellas County Forensic Lab.

In Garon's case, both he and the officer knew that the can of Miller Lite could be a key piece of evidence in a DUI manslaughter prosecution.

The officer tried to secure the can as evidence. Before he could, Garon kicked it over, spilling it onto the sidewalk.

The strategy is this: If you drink after a crash and before a test, it will be harder for police to determine your blood alcohol level at the time you committed the supposed crime.

"We have people who when pulled over for driving drunk … throw the key out of the car and pop open a beer," said Pinellas Park police Sgt. Adam Geissenberger.

This could create a problem for police, because if a blood test shows the person is drunk, how can investigators prove that the alcohol consumed after the crash didn't put them over the limit?

Clearwater defense lawyer Nicholas Dorsten represented Garon. He also represented another client who tried the same tactic.

In that instance, an officer pulled over a St. Petersburg woman on her way home from a Christmas party. The officer called for a member of the DUI unit so they could determine whether the woman had been drinking. Before the other officer arrived, the woman walked inside her home and drank alcohol, Dorsten said. She returned outside in her pajamas and refused a breath test. Police arrested her, but she later was offered a plea deal that reduced her DUI to reckless driving.

Dorsten said prosecutors would have had a hard time proving how much alcohol she had at the time she was pulled over.

In Garon's case, because someone died in the accident, officers had a legal right to test his blood.

An officer stood watch over Garon after he bought the beer. An hour later they drew a blood sample. The test indicated Garon had a .25 blood alcohol level. An hour later officers drew another sample, which read .23. And an hour after that he tested at .21. All are about three times the legal limit.

Garon told officers he had just come from a car show and only had a small glass of red wine. Officers could tell Garon's body had begun metabolizing the alcohol because each blood alcohol reading was lower than the last. This helped save the case.

Garon's blood alcohol level wasn't affected by the beer he drank. If it had, it would have spiked the sample on at least one test.

"What juror wouldn't look at that person and say … 'what the hell is that?' " said Assistant State Attorney Scott Rosenwasser, who prosecuted Garon. "You just killed someone and you're going to start drinking?"

In court, Garon pleaded guilty to DUI manslaughter and vehicular homicide. He was sentenced in June to 17 years in prison.

But if Garon had drunk more immediately after the crash, it could have spiked his blood alcohol level. Would that have made a difference?

"The biggest thing is (drinking after a crash) would have a hard time making a major impact unless there is a significant amount of time and a significant amount of alcohol," said Newman.

Newman said if a person could drink enough, and then wait for the alcohol to kick in, a blood alcohol test would not be able to show their level of intoxication at the time of the crash. That's what might have helped the St. Petersburg woman who drank an unknown amount of alcohol in her home.

Rosenwasser said he doesn't think the tactic works.

"Depending on the blood alcohol level it wouldn't change the way I prosecute," he said. "And in fact, I would use it as consciousness of guilt. They're trying to play a game by drinking it right after."

One thing is clear from Garon's case, and that's that officers should not allow DUI suspects to slip into a convenience store to chug a beer after a fatal crash.

Geissenberger, the police sergeant, said in this case the severity of the crash and the size of the scene made it hard for the officer to give all his immediate attention to Garon. The officer was not disciplined, Geissenberger said, but they did discuss what went wrong.

"It was just about how we as an organization can do better," he said.

Contact Weston Phippen at wphippen@tampabay.com or (727) 893-8321. Follow @westonphippen.