CLEVELAND, Ohio -- The otherwise low-key trial of Cleveland police officer Michael Brelo saw some drama Wednesday, the third day of testimony, when a fellow police officer refused to testify.

Prosecutors got through just a couple basic questions about the identity and work history of Cleveland police officer Michael Demchak before Demchak invoked his Fifth Amendment right against self-incrimination on the witness stand.

According to a report from the Bureau of Criminal Investigation, Demchak was one of 13 officers that fired their guns one night in November 2012, when two unarmed suspects were killed. Investigators concluded Demchak fired his gun four times.

Brelo, 31, is on trial on two counts of manslaughter in the case of Timothy Russell and Malissa Williams, who were shot to death by police in a 1979 Chevy Malibu. Russell, the driver, had evaded police during a 22-minute car chase through Cleveland and East Cleveland on Nov. 29, 2012.

Demchak told the court he invoked his right based on the advice of his attorney and would not testify unless he is granted immunity by the prosecutor's office.

Prosecutors had filed motions before the start of the trial opposing police officers who may invoke the Fifth Amendment. And they were quick to voice their opposition in court as well.

"We don't believe police officers should be granted immunity for testifying," assistant prosecuting attorney Adam Chaloupka told the court. Chaloupka said police officers should trust the Prosecutor's Office to not to charge them for testimony given during the trial.

Cuyahoga County Prosecutor Timothy J. McGinty, who has been present but silent at the proceedings until Wednesday, told the court that as a matter of public policy police officers should be required to testify without being able to demand immunity.

"It won't end with this," McGinty told the court. "I am reluctant to start doing it here and now for fear of the future result."

McGinty also told the court that police officers knew one of their fellow officers did something wrong that night, but refused to come forward with that information to investigators.

Prosecutors have granted immunity to two police officers in the case thus far. Officers Brian Sabolik, who was the first to say he saw Brelo stand on the hood of the victims' car and fire straight down, and his partner Michael Farley have been granted immunity.

But Judge John P. O'Donnell decided police officers have the same right against self-incrimination as any other citizen.

"You're asking a witness to rely on your word that you won't charge him, but that's just not the standard," O'Donnell said.

O'Donnell said Demchak may be called back to testify later in the trial.

The courtroom commotion got a reaction out of the defendant, who has been sitting stone-faced throughout. As prosecutors, defense attorneys and the judge argued about the Fifth Amendment, Brelo smiled slightly and shook his head.

Two other police officers, Wilfredo Diaz and Erin O'Donnell, are expected to invoke their Fifth Amendment rights.

A spokesman for Cleveland Mayor Frank Jackson declined a request Friday for comment on the officer refusing to testify.

Here are other highlights from the trial's third day.

1. The defense argues it's unclear just how many bullets were fired, or where they came from

Wednesday morning, experts with the Bureau of Criminal Investigation testified to the layout of the crime scene. Defense attorneys challenged the prosecution's version of events. Prosecutors have maintained 137 bullets were found, but defense attorneys argued just over 100 bullet holes were identified in the Malibu and two police vehicles nearby. They also argued that trajectories can be determined for only about one-third of the 92 bullets that hit the outside of the Malibu.

2. Police cars are closely tracked

In the afternoon, two experts from CompassCom testified. The company was contacted by the Cleveland police department to interpret auto-location data from the night of the chase and shooting. CompassCom was able to take that data and create several maps and videos showing exactly which police vehicle was where during the 22-minute chase and shooting.

3. What to expect on Thursday

Prosecutors plan to call audio and lighting experts to testify. A video from a Bratenahl police cruiser recorded sound during the shooting. The prosecution has argued that the audio demonstrates a pause between the time most officers realized the threat was over and stopped firing, and the moment when Brelo jumped on the hood of the car and began firing again.