Judge In Zimmerman Trial Bars Audio Expert Witnesses From Testifying

A major evidentiary ruling on the eve of the George Zimmerman murder trial.


In what may turn out to be a key evidentiary ruling in a trial that starts on Monday, the Judge in George Zimmeman’s murder trial is barring the prosecution from putting on expert testimony to  attempt to establish the identity of the person heard screaming on a 911 recording on the night Trayvon Martin was shot dead:

In a major victory for murder suspect George Zimmerman, a judge today ruled that prosecutors may not put on the witness stand two state audio experts who say the voice heard screaming for help on a 911 call was someone other than Zimmerman.

Those screams, recorded while Zimmerman was fighting with 17-year-old Trayvon Martin, are the most dramatic piece of evidence in the high-profile murder case.

Zimmerman, a Neighborhood Watch volunteer, says they came from him, that he was calling for help after Trayvon attacked him. Trayvon’s parents say they are from their son and are his last words before Zimmerman shot him in the chest.

Circuit Judge Debra S. Nelson had heard three days of testimony about the science used by the state’s experts to analyze them. Today she ruled that it failed to meet Florida’s legal standard.

One of the experts, Alan R. Reich, had concluded the voice he identified asTrayvon is heard yelling, “I’m begging you,” and “stop.” The other, Tom Owen, ruled Zimmerman out as the screamer, in part, after using voice recognition software.

Both witnesses are now banned from Zimmerman’s trial, which began two weeks ago with jury selection. Opening statements are set for Monday morning.

The judge barred both experts, she wrote, because prosecutors failed to present competent evidence that the techniques used by Reich and Owen were generally accepted in the scientific field.

The state presented no evidence, except Reich and Owen themselves, who defended their findings, she wrote.

She gave special attention to Reich. None of the five other experts who testified heard the words and phrases that he did, she wrote.

His testimony, she wrote, “would confuse issues, mislead the jury and, therefore, should be excluded from trial.”

The recording is that of a neighbor, who had called 911 to report the fight. The screams and gunshot can be heard in the background.

Four defense experts had challenged Reich’s and Owen’s findings, testifying that using screams to identify someone’s voice is impossible. Valid voice comparisons can only be made if someone speaking in a normal voice, they said.

The judge noted that three of the defense experts, including FBI analyst Hirotaka Nakasone, said they were “disturbed” by the state experts’ conclusions.

Assistant State Attorney Richard Mantei urged the judge Thursday to admit the testimony anyway.

“The evidence should be heard by the jury, and let them decide,” he said.

While I didn’t follow the arguments on this motion closely, what I have read, including the Judge’s 12 page opinion below, indicates to me that the Judge got this ruling largely correct. The purpose of an Expert Witness is supposed to be to aid the trier of fact, whether that be the jury or the judge, in understanding some information that is outside the range of knowledge of the average person. Medical Doctors are frequently Expert Witnesses in personal injury cases, for example, because their specialized knowledge can help the jury understand the relationship between the injuries that the Plaintiff suffered and the facts already established about how the incident alleged to be responsible for those injuries. Medical and forensic experts also frequently testify in criminal trials regarding the evidence found at the scene of the crime, the cause of death, and the approximate time of death based on appropriate medical testing. Uses for experts go beyond the medical field, though, and are often used in cases involving construction, forensic accounting, or any other number of fields where some complex issue plays a key role in the case. Quite often, the opposing side has its own expert witness whose primary task is to attempt to rebut the conclusions being offered by the party who offered the expert testimony.

There are several limitations placed on expert testimony, though. In general, for example, expert witnesses will not be permitted to testify regarding an issue that is supposed to be a question that the trier of fact. For example, so-called “accident reconstruction” experts are generally prohibited from testimony that suggests one party or the other was responsible for a traffic accident, and in some states they are forbidden from testifying at all. Most importantly for this case, though, is the rule that states that any expert testimony with a scientific or technological basis must be ‘generally accepted” in the particular field in which the expert is presented as having expertise. In the case of this Zimmerman ruling, that field would generally be the field of analysis of audio recordings. Given the fact that both the expert presented by the prosecution, who identified that scream as most likely coming from Martin,and the defense expert who identified Zimmerman as the source of the scream, were properly barred from testifying. As noted in the article above and the opinion below, there were four independent experts each of whom stated that it was impossible to make  a determination of who the scream came from with any degree of scientific certainty. The only thing that allowing either, or both, of these experts to testify would have accomplished is to confuse the jury needlessly.

This ruling doesn’t mean that the 911 recording cannot be introduced at trial for the purpose of each side presenting non-expert testimony regarding the identity of the screamer. Indeed, in her order the Judge explicitly states that the recordings can be introduced for that purpose. Most likely, we’ll have the prosecution put Martin’s mother on the stand to say that the screamer’s voice is the voice of her son, while the defense will put on Zimmerman relatives, and likely Zimmerman himself, to say that he is the person screaming. In the end, it will be up to the jury to decide what to believe about that, and they may well decide that both sides witnesses cancel each other out, which would essentially mean that they wouldn’t be giving that much weight to that particular piece of evidence.  For that reason alone, I’d suggest that this ruling constitutes a victory for the defense because all they have to do is create some reasonable doubt regarding the prosecutions case to win.

Here’s the opinion:

Florida v. Zimmerman Order Excluding Expert Testimony by dmataconis

FILED UNDER: Crime, Law and the Courts, , , ,
Doug Mataconis
About Doug Mataconis
Doug Mataconis held a B.A. in Political Science from Rutgers University and J.D. from George Mason University School of Law. He joined the staff of OTB in May 2010 and contributed a staggering 16,483 posts before his retirement in January 2020. He passed far too young in July 2021.


  1. Peter says:

    All I know is that I’m going to be hearing so much about the Blogosphere’s Quasi-Homoerotic Black Male Physical Superiority Fetish that I’ll want to vomit. Blogospherians will take time out from playing WoW in mom’s basement to rhapsodize about the tremendous strength, athleticism, and street-fighting skills of black men.

  2. JKB says:

    Well, following this at Legal Insurrection, the FBI expert as well as others said that they couldn’t isolate a long enough sample (where the scream wasn’t being talked over) to even proceed under their current guidelines. I believe they could get less that 25% of what is normally required. The defense experts repeated the short sample to manufacture a longer sample for their software. Also that the sample did not have enough variety of words and sounds.

    Plus, apparently, there is no body of accepted scholarship in identifying screams, especially when the sample being matched to is normal speaking.

    The real question is why the prosecution kept pushing their expert after he was eviscerated under questioning and basically revealed to be way out from accepted practice.

  3. The real question is why the prosecution kept pushing their expert

    The defense was also pushing their expert who said it was Zimmerman screaming.

    It’s called zealous advocacy

  4. Defense Counsels can go ‘shopping’ for experts until they find one that will say what they want him to. Perhaps Prosecutors can do the same. REGARDLESS, if should have been left for the Jury to decide.

  5. @William Wilgus:

    It has been left for the jury to decide. That’s why the experts were properly excluded.

  6. David in KC says:

    I agree with your analysis on this Doug, it’s a good call by the judge. One little quibble, while I see putting on family members to identify the voice, no way in hell do I put on the defendant. Opens up way to many chance to attack his credibility. Just off the top of my head, I would think the whole bail/money issue then comes in. If he doesn’t testify, it never gets before the jury.

  7. @David in KC:

    The Defendant is, obviously, under no obligation to testify. However, if the defense is going to put on a true self-defense case I cannot see how they can do it without putting Zimmerman on. There are no other eyewitnesses to what happened that night, after all.

  8. David in KC says:

    @Doug Mataconis: Depends, if they can hit the forensics hard enough to show that the could support a self defense, mom on the stand saying its her son on the 911 call, are able to show the victim as violent or something, they may be able to get the jury to vote not guilty. If they think the jury isnt buying the prosecutions story, they don’t put him on. (please note, I am not saying the victim is violent or that this is a real case of self defense, personally, I kind of fall along the side of, why did he continue to follow after the cops said stop. Regardless of what actually appended, if he had done that, everyone would be alive).

    If they do put the defendant on, it’s going to get very entertaining.

  9. @David in KC:

    Granted, whether Zimmerman testifies or not is obviously a decision they are going to leave open until the last possible minute. I will bet you, though, that they have already been hard at work preparing him for the possibility of taking the stand. From what people in the legal profession down in Florida tell me, O’Meara is a pretty smart litigator, there’s no way he wouldn’t be getting ready for the possibility of the client taking the stand.

  10. socraticsilence says:

    @Peter: Its a well known fact that a skinny teenage boy of any race can down an elephant when armed with Skittles and Iced Tea.

  11. For that reason alone, I’d suggest that this ruling constitutes a victory for the defense ….

    How so? Sounds to me like the defense will have plenty of opportunity to inject doubt into the proceedings, but they’re struggling to give it that sheen of “reasonable.”

  12. Jenos Idanian says:

    @socraticsilence: Is that as well-known a fact as the fact that Hispanic men who are 1/4 black are homicidal racists?

  13. JKB says:
  14. anjin-san says:

    Martin was a 160 pound high school football player – its basically as if he had combined DNA from Superman and Bruce Lee…

  15. Dazedandconfused says:

    I’ve been down on voice analysis after seeing Tuiasosopo make a clown out of a highly certified, supposedly ex-FBI analyst in the Te’o scandal.

    I’m thinking the prosecution is on the wrong tack with that stuff. George should be standing trial for exactly what he says happened, if it’s the only thing clearly and easily provable, as it appears to be from the cheap seats. Don’t confuse the jury or the issue. If chasing strangers around at night isn’t an activity that is illegal and/or carry’s responsibility for nearly whatever results from it, so be it.

  16. Caj says:

    In Florida where they have the stupid stand your ground law I feel that Zimmerman has the upper hand! It’s his word against a young man who can no longer speak for himself as he shot him like the profiling stalker he is! I’ll be very surprised if Zimmerman is found guilty. Guns above all else rule in this state!

  17. Matt Bernius says:


    The real question is why the prosecution kept pushing their expert after he was eviscerated under questioning and basically revealed to be way out from accepted practice.

    A statement like this demonstrates a lack of understanding about how modern prosecution and defenses are conducted. Like it or not, the job of the attorney in either case is to push extremely hard for any evidence that has the slightest possibility of having them make their case.

    Typically this sort of stuff is exactly what “law and order” types want to see the prosecution doing and hate when the defense does the same thing. It just happens to be in this case many “law and order” types have decided to side with the defense and so they are *shocked* *SHOCKED!* that a prosecutor would dare sully the office by engaging in this sort of tactics.

    As an aside, it’s exactly these sorts of actions on the prosecution side that lead to many of us being anti-death penalty.

    At least, in this case, it seems like the judge made the correct decision. All too often the prosecution is allowed to move forward with this sort of flimsy “expert testimony.” This, btw, is a good reminder of how important a good defense attorney is in cases like these.

  18. Bob @ Youngstown says:

    I think it was an entirly appropriate ruling (excluding “experts”)

    Let Zimmerman say it was he who was screaming, but also allow Martin’s parents say that they believe it was their son. Then let the jury decide who to believe, or choose not to believe either.

    What for me is more telling is the sequence of events before the shooting. Specifically, that the police told Zimmerman to stop following Martin (“we don’t want you to do that”) and subsequently when Zimmerman was told to meet the police at the mailboxes he said OK, but then later told the dispatcher to have the police call him and he’d tell them (the police) where he was. — Clearly he was indicating that he was going to continue his stalking of Martin.

    I don’t know that Zimmerman is an evil person, I’d even suggest that he had no intention to shoot anyone that night. However, when someone has a gun and is looking for trouble, bad things are likely to happen (intentional or not).

  19. Pylon says:

    As much as I think Zimmerman is likely guilty (But probably will not be bound to be so) I think this is a good decision. I must quibble, however, with the notion that the prosecutor must present a vigorous or zealous case.

    The prosecutor is different from a defense counsel. In theory, they are supposed to present an impartial or dispassionate case and even withdraw charges if they determine that a reasonable doubt standard cannot be overcome. This is why the prosecution must present all of its evidence to defense counsel beforehand whereas defense counsel can retain evidence from the prosecution.

    Of course this is almost never observed in practice.