Nearly a year after a couple were fatally shot by police on Hwy. 212 in Eden Prairie, their families and friends are increasingly frustrated as they await answers while the case remains under review — an unusually long time for an officer-involved shooting case.

In other recent such shootings, investigators and grand juries wrapped up their work within five months or so, according to a review of local cases over the past two years. But the Feb. 7 shooting that killed Matthew Serbus, 36, originally of Maple Grove, and Dawn Pfister, 34, of Elkhorn, Wis., remains under review by the Hennepin County attorney's office 10 months later.

"The family's frustrated," said Robert Bennett, a Minneapolis attorney representing Pfister's family. "There's been no new news. The body of evidence hasn't increased."

The exact point the process is at is not public information. But sources say a grand jury decision could be reached as soon as this month. Bennett has his own theories as to why the case hasn't been resolved yet.

"I'm very sure there is problematic evidence — more problematic than [Eric] Garner or Ferguson, [Mo.]," he said. "This is a harder case than either of those. This is something that should be watched nationally."

Serbus and Pfister were in a stolen car from Colorado when they rear-ended a car on Feb. 7, taking off and leading officers on a chase from Chaska to Eden Prairie. After stop sticks punctured the car's tires, it crashed between Hwy. 101 and Dell Road.

According to an investigation by the state Bureau of Criminal Apprehension, Serbus emerged from the car and "produced a knife," ignoring repeated commands to drop it. After officers fired at him, the BCA said, Pfister "took possession" of the knife, and was shot.

The BCA investigation didn't say how far away the couple were from officers. But police are trained that a knife-wielding person less than 21 feet away can stab an officer before he or she can get a gun out of a holster, law enforcement experts say.

Initial scanner reports called Pfister a hostage, so Bennett said police shouldn't have shot her.

A secretive process

Friends say the couple had returned to Minnesota to face criminal charges for trying to steal a car from a Rochester car dealership. Serbus had a criminal record dating to at least 1999. Pauly Hoffman of Brooklyn Park, a longtime friend, said Serbus wanted to start a new life with Pfister, mother of two young children.

"Not a day goes by that I haven't thought, 'Why the hell haven't they done anything?' " Hoffman said of the process.

On May 28, the BCA finished its investigation and sent its findings to the county to determine if the case should be sent to a grand jury. Since then, no information has been released because grand jury proceedings are secret and protected by law.

Grand juries don't determine guilt or innocence, but rather whether there is evidence of probable cause that a crime was committed that justifies bringing it to trial. In Minnesota, grand juries consist of up to 23 randomly selected people; an indictment requires 12 members to agree.

A Star Tribune review of BCA records last April showed that law enforcement's use of deadly force was justified in 82 of 83 shootings in the past decade. State statutes justify the use of deadly force by law enforcement to protect the officer or someone else from death or great bodily harm.

Thorough or dragged out?

In September 2013, a grand jury cleared officers about four months after the May 2013 Minneapolis officer-involved shooting that killed Terrance Franklin.

It took about five months for authorities to investigate and a grand jury to clear officers involved in an October 2013 officer-involved shooting in Minnetonka that killed 27-year-old Michael Tray.

And it took nearly six months after a November 2013 shooting in Orono for authorities to finish investigating and a grand jury to clear the officers who shot and killed Ted Hoffstrom, 30, after he killed an Orono doctor.

Some cases do take longer, such as the December 2012 case where officers shot and killed a 20-year-old Brooklyn Park man, Melvin Fletcher, after a grocery store robbery in St. Paul. It took nearly a year to investigate and for a grand jury to clear officers.

Derik Fettig, a former federal prosecutor who teaches at Hamline University and the University of Minnesota law schools, said the time a grand jury takes can vary depending on the amount and complexity of the evidence being presented by the county.

"Depending on your worldview, you can say the state [is] being careful and being very thorough," he said, "or could be dragging their feet. We'll probably never know."

Kelly Smith • 612-673-4141

Twitter: @kellystrib