Slager pleaded guilty in May after his murder trial ended in a hung jury. He faces a maximum sentence of life in prison on the civil rights violation.
US District Judge David Norton heard prosecutors contend that Slager maliciously killed Scott on April 4, 2015, and call for him to spend the rest of his days behind bars. Slager's attorneys have painted him as a dedicated and professional former law enforcement officer who'd never exhibited a tinge of racism. The judge will impose the sentence.
The fired North Charleston police officer looked haggard while wearing a striped gray-and-white prison jumpsuit in a federal court in Charleston. His wrists were shackled to his waist.
Slager's parents, his wife and siblings occupied one side of the courtroom's front row; Scott's relatives saw in the other.
The former cop's attorneys sought to convince the court that his actions amounted at the most to voluntary manslaughter.
A probation officer has recommended a sentence of between 10 and 13 years in prison. But federal prosecutors are seeking a life sentence, arguing Slager committed second-degree murder and should also be punished for obstructing justice.
Witness says fight preceded shooting
Fredericks testified that his analysis of video showed Slager and Scott were engaged in an "altercation ... a fight on the ground" before the shooting. But he said he did not see anyone kick or throw a punch.
Fredericks testified that from audio captured by a microphone on Slager he could hear the ex-cop call for backup and tell dispatchers to "step it up."
The witness told the court he could hear Slager tell Scott, "Let go of the Taser before I shoot you." Earlier, Fredericks testified that he heard Scott say, "This is abuse" and "F*** the police."
Under cross-examination by federal prosecutor Jared Fishman, Fredericks said Scott was shot as he was running away from Slager.
"For each and every time he shot at him," the witness said, "he was running away."
He said the former officer later picked up and then dropped the Taser next to Scott's body.
Why drop a weapon by a suspect? the prosecutor asked.
"I don't know of any cases why a law enforcement officer would intentionally move a weapon to a suspect," the witness said.
Slager's voice showed he was psychically tired, winess says
David Hallimore, a forensic audio analyst from Houston who testified for the defense, told the court that he could "clearly hear the exhaustion in Officer Slager's voice" on recordings from that day. He said he interpreted the voice as exhibiting fear and stress.
On Monday, Slager's attorney attacked the credibility of a bystander whose cell phone video captured the fatal shooting and said his client was not a racist.
"Every stop he made had not the slightest implication of any racial implications," attorney Andy Savage said. "Nothing in his background from birth to today shows signs of any racial bias."
Savage presented a letter from an African-American woman thanking Slager, along with video from a traffic stop prior to Scott's stop, that the lawyer said demonstrated Slager's professional tone.
He also noted that most of the DNA found on Slager's Taser belonged to Scott, which he said supported his client's claim that he and Scott tussled over the Taser before the shooting.
Witness: Shooting was an 'abuse'
Feidin Santana -- the man whose cell phone recording captured Slager firing eight times, striking Scott five times in the back -- had a different take, saying he was in shock by what he saw that day.
"It was abuse and something that wasn't necessary," he said, describing Slager's actions.
Santana said he never considered handing over his video to police. He wanted to get the video to Scott's family, prevent it from falling into the wrong hands and protect his own safety, he said.
Lt. Charles Ghent, of the South Carolina Law Enforcement Division, testified that he saw the cell phone video and then interviewed Slager for more than two hours on April 7, three days after the shooting. Savage challenged the thoroughness of that interview.
Ghent acknowledged he did not record the interview or get a written statement from Slager at the time.
Slager was charged with first-degree murder later that day.
During the interview, Ghent said, Slager demonstrated how and he Scott struggled on the ground. Slager said Scott grabbed his Taser and pulled it out of his hand, Ghent testified, but Slager didn't indicate that Scott used the Taser on him.
Slager testified at his trial that he feared for his life because Scott grabbed his Taser.
Slager: 'I knew I was in trouble'
Slager first pulled Scott over for a broken taillight. Moments later, Scott ran away.
A foot chase followed. Slager's first attempt to use the Taser on Scott did not stop him. A second deployment brought Scott to the ground, but he got up and took off again. Slager opened fire as Scott ran away for the final time.
On the stand during his state murder trial, an emotional Slager testified his mind was like "spaghetti"
during the altercation with Scott that day.
He argued that even at 18 feet away, Scott posed a threat and could have turned around and charged him. Prosecutors contended there was little physical evidence of a struggle.
"Scott would never stop after I gave him multiple commands to stop," Slager said in November.
Slager testified Scott was much stronger, and though he couldn't recall all the details, he remembered Scott wresting away his Taser and briefly pointing it at him.
"I knew I was in trouble," Slager said. "I was in total fear Mr. Scott didn't stop, continued to come towards me."
That's when Slager said he pulled the trigger.
Slager's state murder trial ended in a mistrial after the jury failed to reach a verdict last December. Solicitor Scarlett Wilson issued a statement in May, after Slager's plea in federal court
to deprivation of rights under color of law
, saying it was unnecessary for her office to prosecute Slager again.
The sentencing hearing resumes Wednesday morning.