Barrios said witnesses told him that the crash flipped his car three times, and the police crash report states that his Jeep flew into six parked vehicles at a used-car lot next to the gas station. Somarriba’s unmarked police car jumped over a median, according to the crash report.

Somarriba had been involved in two other accidents on the job, both minor, and neither was his fault, according to personnel records. His police department file contains numerous commendations.

Somarriba was the only person airlifted from the scene, while Barrios and Castillo were taken to the hospital by ambulance. Hialeah Fire Department officials have said the way the patients were taken to the hospital didn’t affect their medical outcomes, though family members have questioned that claim.

Surveillance tape from the used-car lot shows a car pulling out of the gas station around the same time as the crash. It is difficult to tell what kind of car is shown. More than 10 seconds later, another security camera shows a car sliding on its roof into parked cars at the lot.

Barrios’ attorney, John E. Leighton, said the lag time between the car leaving the station and the accident is proof that his client obeyed the stop sign just outside the gas station.

Police insisted their detective was not speeding. Lawyers for Barrios’ and Castillo’s families say the damage to the cars suggests otherwise.

Experts said that dozens of calculations go into deducing speed in accidents. Dietrich Jehle is a professor of emergency medicine at the University at Buffalo School of Medicine and Biomedical Sciences. He said that speed is not the only thing that can cause cars, especially SUVs, to roll over.

“If you have an edge that trips you, that’s what starts the rollover process. You can be hit not very hard, but it starts the process,” Jehle said.

Everything, including the temperature outside, the weight of the cars, and even whether a driver should have been wearing eyeglasses, needs to be considered when determining what caused a crash, said Tod Burke, a professor of criminal justice at Radford University in Virginia.

“You don’t want to guess at this. This is science. Wait until the evidence comes in,” said Burke, who also is a former Maryland police officer.

Hialeah police have not let the families or their lawyers download what they say is crucial evidence: information stored on each police car’s “black box,” which would record the speed of the cars right before the fatal crash. Barrios’ mother, Maria, said that when an insurance adjuster inspected the Jeep, it had already been moved, and the police would not let the adjuster see it. The insurance payout from the totaled vehicle would help with Barrios’ medical bills, she said.

In response to what they say is Hialeah’s stonewalling, attorneys for the families filed a complaint in Miami-Dade Circuit Court in November asking for evidence to be released. Both families have notified Hialeah that they will sue the city.

The Barrios and Castillo families aren’t fighting only for evidence to be released, but have also begged Hialeah to turn over its investigation to an outside agency to assure the case is handled without bias in favor of its own detective. The department has refused.

“They made these fast statements without doing any research, and they’re all false. So how can I trust them?” Barrios asked.