As George Zimmerman’s trial entered its second week, more witnesses were called, including Dr. Valerie Rao – a medical examiner tasked with reviewing the video and photographs of the injuries Zimmerman allegedly sustained during the confrontation that led to 17-year-old Trayvon Martin’s death. Dr. Rao testified that, in her expert opinion, the wounds were insignificant and non-life threatening.

ABC News reported from trial’s seventh day.

In her testimony, she contradicts Zimmerman’s claim that Martin slammed his head against the concrete pathway multiple times – a crucial component of the defense’s timeline that will likely have significant bearing on the jury’s assessment of whether Zimmerman’s life was actually in danger.

"Are the injuries on the back of the defendant's head consistent with one strike against a concrete surface?" asked prosecutor John Guy.

"Yes," Rao said.

"And why do you say that?" asked Guy

"Because if you hit the head one time, it is consistent with having gotten those two injuries at that one time," she testified.

Dr. Rao’s testimony is the latest in a long line of evidence intended to bolster or downplay the physical condition in which Zimmerman was initially booked following the shooting. If the prosecution can convince the jurors that Martin did not pose a threat for the defendant, Zimmerman can be convicted of second-degree murder. Conversely, if the defense can show that their client experienced a situation where his life was clearly in danger, they can defer to Florida’s stand-your-ground statute, whereby an individual is entitled to exercise self-defense without an obligation to retreat first.

"If you look at the injuries they are so minor they are not consistent with grave force," Rao said. "If somebody's head is banged with grave force I would expect a lot of injuries. I don't see that."

Tuesday also saw the testimony of Zimmerman’s friend Mark Osterman, as well as the long and tortuous cross-examination of Chris Serino – the lead investigator in the case, who initially considered Zimmerman’s version of the story believable.

"If we were to take pathological liar off the table…do you think he was telling the truth?" asked defense attorney Mark O'Mara.

"Yes," responded Serino.

The prosecution moved to strike Serino’s comment from the record, which was sustained by Judge Debra Nelson, who ruled that the witness could not offer an opinion of another.