Cooper Harris' lifeless body was covered in discolorated skin from pooled blood and had numerous abrasions the Cobb County medical examiner testified on Tuesday.

Graphic images shown to the jury by the examiner illuminated the extent of the toddler's injuries — creating an emotional morning of testimony in the hot car murder trial. Justin Ross Harris is charged with murder in the death of his 22-month-old son who he left in a hot SUV to die in June 2014. The defense maintains it was a tragic accident.

Here are three key developments from Tuesday’s testimony.

1. ‘He probably would have struggled’

Harris broke down repeatedly Tuesday as prosecutors detailed his son’s final hours, in pictures and words.

At least one of the jurors was also overcome with emotion as former Cobb County Medical Examiner Brian Frist described the agony experienced Cooper in the backseat of his father’s SUV. His death was not quick, Frist said. Just how long it took is unknown.

Cooper experienced a wide array of maladies as his organs began to shut down, Frist testified.

“The phases he would have experienced, could have experienced, likely included nausea,” he said. “He would have had a headache. He would become dehydrated. He may have had seizures. He probably would have struggled as he was becoming more and more uncomfortable.”

2. ‘(Cooper) could have survived that’

The former medical examiner said there was a possibility that Cooper could have still been alive at lunchtime the day of his death when Harris opened his car door to throw a bag of light bulbs he had bought at Home Depot on the front seat.

Frist said he was told by a Cobb police officer that the temperature inside the car remained in the low 90s throughout the morning of June 18, 2014.

“(Cooper) could’ve survived that,” Frist said. Whether he was still alive when Harris stopped by his car about three hours and 15 minutes after leaving his son locked inside remains a mystery. The high temperature that day reached 92 degrees outside; some estimates had the temperature inside the 2011 Hyundai Tucson at or near 140 degrees.

3. Did he see Cooper?

Jurors watched surveillance video from the Home Depot office parking lot that showed Harris leaving his son in his SUV, returning to his car at lunchtime and then driving away from work that afternoon.

In one snippet, he passes an open space, backs up and then drives in and parks at 9:25 a.m. Harris had just returned from a nearby Chick-fil-A where he and Cooper ate breakfast. The video shows that Harris sat in his car for 33 seconds before exiting the vehicle.

Questioned by defense attorney Carlos Rodriguez, witness Greg Sanders, a security officer for Home Depot, acknowledged that Harris never bent down far enough to get inside his SUV and that he didn’t stick his head inside.

“He didn’t get in, he didn’t sit down in the car,” Rodriguez began. “He didn’t get into the car,” Sanders agreed.

Harris’ head never goes below the roof line, Rodriguez added. Sanders agreed. “The head is out,” he said.

The point is important because if the video showed Harris leaning inside his car and looking inside, he would have had to know Cooper was inside.

4. Relaxed and nonchalant?

Harris seemed nonchalant while he waited in the Cobb Cobb Jail’s holding area, according to a witness that testified.

Jail surveillance video taken after he was arrested shows Harris appearing composed and relaxed. Witness Mark Wilson, in jail for a DUI, said Harris engaged in small talk and didn’t act like someone who had just lost a child.

Cobb police decided to charge Harris because they found his behavior off-putting following Cooper’s death. Prosecutors have attempted to make that point throughout the trial, with mixed results. Their latest effort was likely undermined by Wilson’s admission that he had sold his account to The National Enquirer for $2,000. And, as defense attorney Carlos Rodriguez noted, the footage from inside the Cobb jail was cherry-picked and contained no audio.

You can follow minute-by-minute developments in the trial at AJC.com and on Twitter at @AJCBreakdown. AJC reporters Christian Boone (@reporterJCB) and Bill Rankin (@ajccourts) will be in Brunswick for the duration of the trial.

Harris is also the subject of the second season of the AJC's podcast series "Breakdown," which will follow the trial's developments.