An Arizona Supreme Court ruling issued Thursday allows the state to be sued in the 2009 death of a Tucson-area woman killed when a motorist slammed into an Arizona Highway Patrol officer's car where the woman was in custody during her DUI arrest.

The justices' unanimous ruling narrowed lower courts' interpretations of a state law that provides the state and its local governments with partial immunity from injury suits involving drunken or reckless drivers.

The lower courts had said the law applied although Faith Mascolino, 45, wasn't behind the wheel when she was fatally injured, but the Supreme Court said Arizona's long-established state policy was to interpret immunity laws as "restrained and narrow."

Therefore, the Supreme Court said, the immunity law only applies to injuries suffered by a driver while actually "driving or in actual physical control of a motor vehicle."

The Supreme Court's interpretation "represents a narrower view of the statute, without undermining the Legislature's grant of qualified immunity," Justice John Pelander wrote for the court.

A conservator for Mascolino's surviving minor children had sued the state and the other driver.

Jurors who were informed of the immunity law returned a verdict in favor of the conservator, but found that only Mascolino and the other driver were responsible. They attributed 25 percent of the fault to Mascolino and 75 percent to the other driver.

Mascolino was pulled over on an Interstate 10 overpass early the morning of June 3, 2009, after a Highway Patrol officer saw her vehicle drifting across lanes and traveling well below the speed limit.

She was arrested after one officer observed signs of intoxication, she was unable to complete field sobriety tests administered by a second officer, and a breath test found she had a blood-alcohol level over the legal limit.

One of the officers was calling Mascolino's family to arrange to have her car picked up when the officers saw a car coming toward them. The officers jumped over the guardrail as the car crashed into the cruiser, which exploded and burned, killing Mascolino.

A manslaughter charge against the other driver, Robert Gallivan of Tucson, was dismissed in 2011 at the request of prosecutors who said there was little chance of conviction.

The lawsuit case now returns to trial court for further proceedings.