The Trayvon Martin 911 call has become a focal point of the George Zimmerman murder trial, the live stream of which continues Tuesday in Florida.
Persuading jurors about who is shouting on the 911 call that captured the fatal confrontation has become the primary goal of prosecutors and defense attorneys alike.
Watch the George Zimmerman trial live stream below:
Jurors on Monday were presented with conflicting testimony about whether Zimmerman's and/or Martin's voice could be heard screaming for help.
A parade of Zimmerman friends said they recognized his voice.
Martin's father, who police said initially told them he did not recognize the voice, said he came to realize it was his son after hearing the tape some 20 times.
Earlier in the day, the judge ruled that defense attorneys may present evidence to the jury that Martin had marijuana in his system when he died.
Judge Debra Nelson denied a motion by prosecutors to keep toxicology results showing THC in Martin's system at the time of his death from the jury.
Late Monday, Zimmerman defense spokesman Shawn Vincent said the defense could rest by the end of the day Tuesday or early Wednesday morning.
The prosecution would then get to call their rebuttal witnesses, with closing statements by Thursday or Friday if everything goes according to plan.
It's unclear if George Zimmerman will testify in his own defense, but the better his team feels its chances are, the less likely that scenario becomes.
His entire case depends on whether he can convince the jury that he acted in self-defense and that Trayvon Martin was the aggressor in the altercation.