The last in a series of pre-trial hearings will have a huge impact on what evidence the jury is allowed to hear when George Zimmerman goes on trial for second degree murder next week.
Zimmerman is accused of shooting 17-year-old Trayvon Martin at close range in Sanford, Fla. in February of last year.
The former neighborhood watch volunteer has pleaded not guilty and maintains he acted in self defense after Martin attacked him.
One of the biggest issues still up in the air is whether or not the jury will hear a 45 second 911 call placed the night of Trayvon's death.
Screaming can be heard in the background of the tape but voice recognition experts are conflicted about whose voice it is.
Prosecutors - who say the screaming voice is Trayvon - want the call played in court. Zimmerman's defense team say that it can't be proved whose voice is on the tape and it should not be admissible in court.
On Thursday, Hirotaka Nakasone, a senior voice-recognition scientist for the Federal Bureau of Investigation who analyzed the audio, testified for the defense.
Only three seconds of the audio was just the screaming alone, without any other voices or background noise, which Nakasone said is not enough to match it to either Trayvon or Zimmerman.
And the "distress" in the voice rendered it unable to be compared with "reasonable, natural speech."
No witnesses for the prosecution have testified yet. According to the Orlando Sentinel, the most influential and definitive of the state's experts is forensics consultant Alan R. Reich.
Reich said he hears Zimmerman make a "seemingly religious" proclamation while, simultaneously, Trayvon cries out "I'm begging you."
Reich also says the last cry before the shot was Trayvon, yelling the word "stop."
Zimmerman’s lawyers will fight to have Reich's analysis thrown out.
Robert Zimmerman, Zimmerman’s brother, told CBS News on Wednesday that Reich "is hearing what no one else is able to hear."
"Experts that reach conclusions that can’t be re-created by any other person flies in the face of the very definition of science," Zimmerman said.
Seminole County circuit judge Debra Nelson is expected to rule on whether the 911 tape will be played in court on Friday.
If allowed,the 911 tape could be a key piece of evidence for the prosecution.
Earlier this week, the judge threw out a long list of potential evidence including a series of texts, social-media conversations, and photos that show Trayvon referencing pot and guns.
The evidence can not be used in the opening statements but Nelson left the door open for it to be admissible at a later point.
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