What Mark Osterman and his wife, Sondra, write in “Defending Our Friend: The Most Hated Man in America” isn’t exactly new. Their book on George Zimmerman, the killer of Trayvon Martin, is an amplification of what Mr. Osterman told agents from the Florida Department of Law Enforcement (FDLE) on April 26. Zimmerman and his wife stayed with his mentor, a former Seminole County deputy, in the weeks after the Feb. 26 shooting.

But Osterman’s retelling of Zimmerman’s retelling of the tragic event raises serious questions about what really happened that rainy night. Chief among them: Where is the DNA evidence to corroborate Zimmerman’s story? For a man claiming self-defense in a life-and-death struggle, there appears to be precious little of it.

We know what Zimmerman says happened: Trayvon punched him in the face. There was a struggle, but the unarmed 17-year-old got on top of the 28-year-old and started slamming his head into the concrete. Curses were hurled. A flurry of punches were thrown at Zimmerman’s head and face by Trayvon. Zimmerman’s mouth and nose were covered by Trayvon. Zimmerman said he shot the teenager before he could get a hold of the neighborhood watch volunteer’s gun.

In that April interview with police, Osterman added some details Zimmerman had not. According to the report from FDLE, Osterman said that Trayvon “then observed or felt the handgun on Zimmerman’s side, took his other hand away from Zimmerman’s nose and reached for the handgun stating, “You’re gonna die tonight, m-----f-----.” Zimmerman then “slapped Martin’s hand away from the handgun, rotated the weapon and fired one round.”

In Osterman’s book, this detail is added to the Zimmerman recounting.

Somehow, I broke his grip on the gun where the guy grabbed it between the rear sight and the hammer.

The DNA evidence released by the prosecution two weeks ago revealed that Trayvon’s DNA was not on Zimmerman’s gun. Actually, that evidence had been among DNA evidence released earlier. Its significance was lost on me then. But given all that we know now, those DNA reports are a treasure trove of information that collectively raise more questions about (or poke more holes in) Zimmerman’s story.

Trayvon’s hands — how they were found versus what Zimmerman said he did with them — have long fascinated me. Now, there’s Trayvon’s fingernails.

This Feb. 27 photo released by the Florida State Attorney's Office shows George Zimmerman, the neighborhood†watch volunteer who shot Trayvon Martin, with blood on the back of his head. ((AP Photo/State Attorney's Office))

For all the punching claimed by Zimmerman and the injuries he suffered — the bloody nose, the bloody back of the head — “Exhibit ME-12,” Trayvon’s hoodie, had no traces of Zimmerman’s blood on it. There were three stains, two of which “gave chemical indications for the presence of blood.” Only one had a partial DNA profile that matched Trayvon. The right cuff, left cuff and lower sleeves of both arms of the hoodie found “No DNA results foreign to Trayvon Benjamin Martin....”

Of the four stains that “gave chemical indications for the presence of blood” on “Exhibit ME-8,” the shirt Trayvon wore underneath his hoodie, only one matched Zimmerman. Two matched Trayvon. The major and minor contributors for the fourth stain “could not be determined.” The right cuff and lower sleeve of the shirt had no DNA “foreign to” Trayvon. The left cuff and lower sleeve had “the presence of at least two individuals.” It is “assum[ed]” that Trayvon is the major contributor. But because of “the limited nature of the results . . . no determination can be made regarding the possible contribution" of Zimmerman to that DNA mix.

According to Kendall Coffey, former U.S. attorney for the Southern District of Florida, under normal circumstances, “ambiguities about DNA evidence favors the defense.” But he added, “This case has a distinction. That George Zimmerman says Trayvon Martin was trying to kill him. In a self-defense case, ambiguities in DNA can undermine a case of self-defense.”

Those ambiguities that undermine Zimmerman’s claim of self-defense don’t only apply to Trayvon’s clothing. They apply to Zimmerman’s, as well. And as you’ll see in my next blog post, the case where nothing makes sense — nothing — makes even less sense.