Unless they can reanimate Trayvon’s corpse there is no way to prove it was his scream. Tom Owen is just doing his best Brian Meehan impersonation trying to get some extra court business.
Yet standards set by the American Board of Recorded Evidence indicate "there must be at least 10 comparable words between two voice samples to reach a minimal decision criteria." While Zimmerman says more than that many words on his 911 call, the only one heard on the second is a cry for "help."