Prosecutors in the case of a Minneapolis police officer who shot unarmed woman Justine Damond-Ruszczyk are pursuing what could be a key element of defence.
That element is whether accused officer Mohamed Noor heard a loud slap against his police SUV that stirred fears of an ambush.
The prosecution has tried to raise doubts about whether that slap occurred and attacked officers and investigators for apparent missteps.
They have noted that police at the scene turned body cameras on and off at will, did not share information and possibly disturbed evidence, according to court testimony.
Noor, 33, is on trial for murder and manslaughter in the July 15, 2017, death of Ms Damond, a 40-year-old dual citizen of the US and Australia who reported a possible sexual assault in the alley behind her home.
She was fatally shot after she approached the police vehicle.
One point of contention is whether Ms Damond slapped the SUV, causing a thump that Noor's partner, officer Matthew Harrity, testified scared him so much that he drew his weapon.
Defence lawyers for Noor have said he also heard a loud bang on the squad car, but prosecutors have suggested the slap was concocted. They insist the officers faced no threat.
Officer Harrity testified that he did not tell anyone about the thump on the night of the shooting.
The first time he spoke about a noise was three days later, when he sat down for an interview with his lawyer and state investigators.
But somehow, the notion that Ms Damond slapped the car made its way into a search warrant affidavit hours after the shooting.
"There was a conspicuous absence of information," Chris Olson, assistant agent in charge of the state Bureau of Criminal Apprehension, testified this week.
As he was trying to figure out what happened, Mr Olson said, the scene's incident commander, Minneapolis police Sergeant Shannon Barnette, told him she had a brief conversation with Officer Harrity, and that it sounded like Ms Damond had made contact with the car.
Bradford Colbert, a law professor at Mitchell Hamline School of Law in St. Paul, said that under law, Noor had a right to use deadly force to protect himself or others.
For prosecutors, Mr Colbert said, the preferred narrative would be that Ms Damond was shot after merely appearing at the window. For the defence, it would be better if MsDamond slapped the car, creating the loud, startling noise.
"I can see why the state would be arguing or trying to convey that there was no slap," he said.
Jennifer Kostroski, a BCA latent print examiner, testified there was no forensic evidence to show Ms Damond touched the squad car. But under questioning from the defence, she said knuckles or a backhand slap would not leave prints.
Other witnesses said the squad car was partially dusted for fingerprints - but not entirely - then sent to be washed just hours after the shooting.
The trial has revealed other apparent missteps by investigators.
Some Minneapolis police officers turned their body cameras on and off, so it's possible that key statements went undocumented.
One officer was not told that Noor fired from inside the vehicle, so he entered the car and possibly disturbed evidence.
Australian Associated Press