POLK COUNTY, Fla. -- Deadly hit-and-run crashes are all too common in the Bay Area, and sometimes even when investigators have located the vehicle involved in the crash it can take months to make an arrest.

• Troopers say it takes time to investigate hit-and-runs
• Can take months to get lab results from crash scene
• Proving who was driving can go beyond DNA

"People need to understand these things take time," said Sgt. Steve Gaskins with the Florida Highway Patrol.

FHP is working two such cases from early May. One was in Hillsborough County and the other was on Interstate 4 in Lakeland. 

In one of those cases, an attorney for the owner of the vehicle involved in the deadly crash came forward to say where investigators could find the vehicle.

Even after locating their suspected vehicle, it can take months to get lab results from the crash scene back from the Florida Department of Law Enforcement.

"Where they do the forensic comparison of the paint chips from the vehicle that we take to the paint chips that we find on the victim's clothing," said crash investigator Corp. Travis Donakowski. 

But it's another step to prove who was driving the vehicle. 

"Our issue that comes into play is that we have to put that person behind the wheel of the car at the time of the crash and that can be very complex," said Gaskins. 

The driver's DNA in a vehicle doesn't even prove who was driving. After all, you would expect the owner's DNA to be in the car. But that doesn't prove they were driving at the time of the crash. 

But Gaskins said DNA on a deployed air bag might be enough. "During a crash event where that air bag comes out, it's going to collect clothing samples, minute clothing samples, DNA, that kind of information.”

Sometimes the drivers tell things to friends, relatives and coworkers and they come forward. "Even if you don't think it applies, maybe, or you are unsure, give us that information because that could be the one piece of the puzzle that opens up the door to something else," said Gaskins. 

Some drivers who don't confess seem to think they might get away with a hit and run by waiting out investigators.

"They can feel that way but that's not the case," said Donakowski. "We're going to get them in the end. No matter how long it take we are going to prove they are the driver of that vehicle."

FHP is asking anyone who has information on hit-and-run crashes to call them or Crimestoppers.