Advanced technologies shed more light on the killing of Trayvon Martin

findings. The Michigan-based audio engineer and forensics expert used audio enhancement and human analysis to arrive at the same conclusion.

Some experts, however, point out that there is an inherent unreliability in voice biometrics because the voice can be altered by such factors as age or emotional state.

While one advanced technology — voice biometrics — appears to undermine Zimmerman’s story, another may appear, on first blush, to support it.

The Sanford Police Department released the original surveillance video of Zimmerman’s arrival at police headquarters. The somewhat grainy video showed no injury to Zimmerman consistent with his account of the incident.

Since that time, ABC News contacted Forensic Protection, Inc. to process the released video recording for clarification. Following the enhancement process of redigitization, the video shows some kind of injury to the back of his head, which was invisible in the original video because of the poor quality.

Forensic experts who examined the redigitized video say, however, that, if anything, this new piece of visual evidence further undermines Zimmerman’s version of events.

On a CNN news show, Lou Palumbo, a retired Nassau County police investigator with more than thirty years experience in forensic investigations, pointed out these issues:

1. Zimmerman, to accentuate his argument that his life was in danger, said Martin punched him the nose and broke it. Yet, the front of Zimmerman’s shirt and jacket are clean, without any indication of  the blood stains typically associated with a profuse nose bleed, which a broken nose would generate.
2. What may appear like an injury to the back of Zimmerman’s head could not possibly have been a “life threatening” injury:  the police report talks of police officers helping Zimmerman “clean up” — a language used to describe little bleeding from shallow scratches, not life-threatening wounds (this is consistent with the fact that one of the calls by the police to an EMS crew to rush to the scene was cancelled after Zimmerman was found not to require emergency treatment)
3. Zimmerman was brought to the police station within minutes of his altercation with Trayvon — yet he gets out of the police car on his own, walks about unaided and upright, his gait is steady, he does not limp or stagger or stumble, and he is alert and responsive. This is not the manner in which an individual who, only minutes earlier, was engaged in a life-or-death struggle and who sustained life-threatening injuries, carries himself.
4. Palumbo says that to any trained police eye, the video offers an incontrovertible proof of how light and insignificant Zimmerman’s wounds — if, indeed, he had sustained any: the police officers bringing the hand-cuffed Zimmerman to the police station and guiding him from the squad car into the building, do not wear gloves. Palumbo says that police officers who arrest a wounded suspect who had sustained any kind of injury, always wear gloves. The bleeding may have been stopped be a medical crew on the scene, but if the suspect’s cloths have any amount of blood on them — or if the blood is not visible but the police officers suspect that there is blood on the cloth owing to the injuries the suspect sustained — it is mandatory for the officers to wear gloves while handling the suspect. This is done not only for self protection (the suspect may be infected with a contagious disease), but for evidentiary purposes: the blood on the suspect’s body and cloths would be analyzed for forensic evidence such as DNA, and police officers are on guard not to compromise this evidence by contaminating it. There are three or four police officers handling Zimmerman  — a couple in the car bringing Zimmerman from the scene of the shooting to the police station, and one or two waiting for him as he gets out of the squad car. None of them is wearing gloves.

After the initial reaction to the video as offering support for Zimmerman version, many — especially those with police and forensic experience — now claim that it offers further evidence that the Sanford police, out of either incompetence or bias, botched the investigation of the case from the beginning.

Some say it is both, and point out to this fact:  when police officers arrived on the scene, they drew blood from the body of the dead Trayvon and sent it to the lab for examination of alcohol and drug contents. No blood sample was drawn from Zimmerman, and he was not checked for the presence of drugs or alcohol in his system.