SANFORD, Fla. — The screams are clearly coming from a distraught male, whose repeated cries for help end abruptly with a gunshot. What is not clear from a recording of a 911 call, however, is the identity of the screamer: George Zimmerman, the volunteer community watchman, or Trayvon Martin, the unarmed 17-year-old he killed that night.
While jurors in Zimmerman’s second-degree-murder trial, in which opening statements are scheduled for Monday, may get to hear the recording in court, they will not hear the opinions of two audio experts for the prosecution about who the screamer is, or is not. One concluded that the voice was not Zimmerman’s; the other said it was very likely Martin’s.
In an order released Saturday, the judge in the case, Debra S. Nelson, excluded their testimony. She said the science supporting the experts’ analyses “is not as widely accepted at this time” as the more established methods relied on by defense witnesses who said it was impossible to conclude whose voice it was.
A neighbor made the 911 call on Feb. 26, 2012, during the fatal encounter between Zimmerman, who is Hispanic, and Martin, who was black and was returning, after buying snacks, to a home where he was staying. Zimmerman claimed self-defense and was not arrested for six weeks, setting off protests nationwide.
The opinions of the state experts were crucial to the prosecution’s case because they cast doubt on Zimmerman’s insistence that he fired the gun in self-defense. The defense said that the testimony would only confuse the jurors, and that the science behind the prosecution experts’ techniques was faulty.
In days of pretrial hearings, prosecution lawyers pushed hard for the inclusion of their two experts.
One, Thomas J. Owen, a forensic audio consultant, compared the 911 recording with clips of Zimmerman’s speaking voice and concluded that it was not the defendant who was screaming. The second expert, Alan Reich, a forensic acoustics consultant, said that the screams had most likely come from Martin, and that he could also discern the teenager pleading, “I’m begging you.”
But four experts presented by Zimmerman’s lawyers, including one expert from the FBI, said it was impossible to determine who was screaming because of the recording’s limited quality and brevity. They also sharply questioned the methods used by both of the prosecution’s experts.
Peter French, president of the International Association for Forensic Phonetics and Acoustics, said he had never heard of comparing a screaming voice with a normal voice for identification. Another expert, George Doddington, a scientist who has worked with the National Security Agency, said Reich’s claim of hearing “I’m begging you” was “imaginary stuff.”
Under the law, experts’ opinions based on a technology or a scientific technique can be admitted as evidence only if that technique is “generally accepted” in their field. The defense lawyers successfully argued that evidence from the prosecution’s audio experts did not meet that standard.
In another ruling, issued Friday, Nelson turned down the defense’s request that the state not use the terms “wannabe cop” and “vigilante” in opening statements. She also ruled that the state could say “profiling” but not “racial profiling.”