Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

Several pieces of evidence weren't tested and others were missed after white South Carolina cop Michael Slager shot and killed black motorist Walter L. Scott as he was running away, a state investigator testified Wednesday at Slager's murder trial.

A video made by a bystander showing Slager shooting Scott in the back in April 2015 stunned the nation and led to murder charges for the former North Charleston police officer, who could be sentenced to 30 years to life in prison if he's convicted.

Jamie Johnson, an agent for the State Law Enforcement Division who arrived on the scene the day of the shooting, said under cross-examination from Slager's attorney, Andy Savage, that "several" pieces of evidence were never tested, NBC station WCBD of Charleston reported.

The Morning Rundown Get a head start on the morning's top stories. This site is protected by recaptcha

Crime scene investigator Jamie Johnson presents evidence Wednesday at the murder trial of former North Charleston police Officer Michael Slager in Charleston, South Carolina. Pool / Getty Images

She acknowledged that it was the defense team, not official investigators, that uncovered additional "projectiles" at the scene two weeks later, The Post & Courier newspaper reported.

Former colleagues have testified that Slager told them that Scott managed to wrestle his Taser away from him and pointed it at him, prompting him to fire his service weapon.

The defense argues that the Taser wasn't fully tested to determine specifically where on the Taser Slager's and Scott's DNA was deposited. Johnson acknowledged Wednesday that SLED was able to confirm only that both men left DNA somewhere on the weapon.

Tuesday, Almon Brown, another state crime scene investigator, testified that he was concerned when he examined Scott's body because what he saw didn't match what he had been told about how Scott died.

Scott's wounds "seemed to be in the back and side and didn't seem to be correct," Brown said.