Testimony in the murder trial of former Minneapolis police officer Mohamed Noor is nearing completion in its fourth week as prosecutors prepare to call expert witnesses to the stand Wednesday, capping off more than 50 people who have testified in court.

Attorneys on Tuesday began finalizing instructions that will be given to jurors before they deliberate, signaling the end of a trial that grabbed international headlines and focused heavily on alleged missteps by Minneapolis police and state investigators. Defense attorneys have three experts on their witness list who could testify after prosecutors rest their case; it remains unknown whether Noor will testify about why he fatally shot Justine Ruszczyk Damond in 2017.

The prosecution aggressively questioned the Minnesota Bureau of Criminal Apprehension (BCA) Tuesday about its inquiry into Damond’s killing and role in perpetuating the theory that she slapped Noor’s squad moments before he fatally shot her. The prosecutors’ case on authorities’ shortcomings had previously been directed at Minneapolis police.

BCA Assistant Special Agent in Charge Chris Olson testified Monday that Minneapolis Sgt. Shannon Barnette introduced the word “slap” into the investigation. His testimony resumed Tuesday, during which he admitted that he instead could have been the source.

Assistant Hennepin County Attorney Amy Sweasy asked Olsonwhether, in a meeting with prosecutors earlier this year, he told them that Barnette had said that Noor and his partner, Matthew Harrity, were “startled” at the scene.

Reading aloud from a transcript of that meeting, Sweasy asked Olson if he admitted to asking Barnette, “Could it be like a slap?”

“Yes, that’s possible,” Olson said.

The prosecution has asserted that the slap was invented by Barnette and Olson, and perpetuated by the BCA, which investigates officer-involved shootings, in two search warrants and a news release to the media.

A forensic scientist testified Monday that Damond’s fingerprints did not match 51 prints lifted from the squad.

Sweasy also questioned Olson’s treatment of a neighborhood woman who came by the shooting scene the morning after and told him that she thought Damond could be the subject of three 911 calls she had made the previous night.

Olson testified that he told the neighbor that the subject of her 911 call was likely “not relevant” to the death investigation. The neighbor had called about a woman with possible dementia walking near Damond’s south Minneapolis home.

“Was that a good time to start deciding whether things were or weren’t relevant to this investigation?” Sweasy asked.

“No,” Olson said.

Olson testified that the BCA did not investigate the neighbor’s 911 call or determine which officers had responded to it. But, he said, he changed his mind about the call’s relevance once Nancy Dunlap, an investigator with the Hennepin County Attorney’s Office, informed him that Noor and Harrity had responded to the neighbor’s call.

Prosecutors have argued that the neighbor’s 911 call and Damond’s 911 call later the night of July 15, 2017, should have put Noor and Harrity on alert that they were likely to encounter a victim or 911 caller and not a threat the night Damond was killed.

Noor and Harrity were responding to Damond’s 911 call about a possible sexual assault in the alley behind her home when the officers, according to defense attorneys, were “spooked,” according to Harrity, by a loud sound on their squad and a dark figure at Harrity’s driver’s side window, prompting Noor to fire from inside the vehicle about 11:40 p.m.

While Olson said the BCA conducted a “robust” canvass of the neighborhood to investigate what caused Damond to call 911, he acknowledged that the agency did not check other police calls to cross-reference them or check hospitals for possible assault victims.

“Did you find out later that someone did do that work?” Sweasy asked.

“Your investigator,” Olson said.

Dunlap previously testified that she was unable to identify what had alarmed Damond.

Under cross-examination by defense attorney Thomas Plunkett, Olson testified that a neighbor told him that noise from a “family of raccoons” could have been the source of Damond’s concerns.

But Olson said that he didn’t follow up on that information, either.

“You didn’t interview the raccoons?” Plunkett asked.

“Correct,” Olson responded.

When Plunkett inquired as to why Olson hadn’t investigated the tip about the woman — who was last seen at a bus stop — wandering the neighborhood, Olson said he didn’t see a connection.

“In your 25-year career in investigations, have you determined that people at bus stops get on buses?” Plunkett asked. Olson agreed.

Sweasy also pressed Olson about why he allowed Harrity to be interviewed at his attorney’s home instead of at BCA headquarters.

She was critical of how BCA investigators waited to speak with Harrity until three days after the shooting, a concession Olson admitted was not afforded to civilians in homicide cases.

“I would prefer that the interview take place at a different venue,” Olson said.

“Why is that?” Sweasy asked.

“Because of perception,” Olson answered.

“And what perception is that?” Sweasy asked.

“The perception of my having to answer your questions here today,” he said.

Could it look like “special treatment?” Sweasy asked.

“I believe it can, yes,” Olson said.

Joseph Coiro, who worked for a Pittsburgh-based company contracted by the BCA, also testified that gunshot residue was found on the squad’s driver’s side ceiling, interior driver’s side door and driver’s side dashboard.

Coiro said it was also found on the front of Damond’s shirt and sleeves; Harrity’s shirt, vest and pants; and Noor’s pants.