The cries for help heard on a 911 call the rainy February night George Zimmerman shot Trayvon Martin were once again in focus in a Sanford courtroom Monday night.

Zimmerman, a Sanford neighborhood watch coordinator said he killed the unarmed Miami Gardens teenager out of self defense.

The question has always been who is screaming on that recording: George Zimmerman or Trayvon Martin?

The FBI has already said its technology could not determine whose voice it is. Potential jurors who've heard the call also find it difficult to decipher. Take potential juror H27. He described himself as "pro-Zimmerman" during questioning on Monday, even donated to the defendant's defense fund, but when it came to that 911 call he said he couldn't take a side, "I find it is hard to tell which is which".

Yet prosecutors found an audio expert who claims to know exactly who it was. Alan Reich produced a controversial report that not only found Trayvon Martin to be the source of the screaming, but also told the court he could hear the late teen saying "I'm begging you". Reich is the only audio expert we've heard from that can identify speech in the seconds of screaming.

Monday afternoon's hearing is about picking apart the science.

Joining the courtroom via Skype was defense expert James Wayman who said Reich did not provide enough detail in his report to figure out exactly how Reich came to his conclusions. "It's like magic" he said.

Judge Debra Nelson will have to decide whether the science utilized by Reich was "new or novel" or generally accepted by the scientific community.

Orlando-based criminal defense attorney Lyle Mazin told Local 10's Christina Vazquez, "In this specific case the reason it is challenging for voice recognition is that the sample that they had was exceptionally short."

Voice recognition is politely called a "soft science", callously referred to as "junk science" by certain legal observers.

Mazin explained how voice recognition technology is different from fingerprints or DNA, "DNA or fingerprints can be broken down to an actual probability, that it actually matches the person's DNA and that's a scientific calculation. With voice recognition its merely an expert's opinion."

The defense's end game in this hearing is to convince the Judge to toss Reich's testimony out of trial.

Mazin said whatever she decides will have a significant impact on the state's case. "Candidly, it's very important," he explained because in his view the state has, "very limited evidence in this case, not a lot of hard evidence in this case. One of the things that is available to the state here, scientifically speaking of course, is the voice analysis. If they can at least have some sort of forensics to present to the jury it makes their case stronger."