The Trayvon Martin case has exposed some of the media's worst tendencies--selective editing, rushing to judgment, stoking anger for ratings and page views--and it's taken more than fake photos, the incendiary stumbles of Geraldo Rivera and Spike Lee and verbal clashes between Piers Morgan and Toure to shine a light on them.

Here are three recent, troubling examples:

1. After ABC News aired surveillance video of George Zimmerman, Martin's shooter, entering a police precinct without any apparent injuries, the Daily Caller treated the tape like a Zapruder film, enhancing still images from the video and concluding that it found "what may be an injury to the back of his head." The site's photo "analysis" of the back of Zimmerman's head--replete with yellow Photoshopped arrows--"indicates what appears to be a vertical laceration or scar several inches long."

Keep in mind, this is the same Daily Caller that published 152 pages of what the conservative site claims were Martin's tweets--which, if they were, prove that Martin was a pretty typical high school male, preoccupied with girls, sex and getting out of class early.

2. NBC told the Washington Post that it has launched an internal investigation of the "Today" show's editorial process after its morning show aired an edited conversation between George Zimmerman and a 911 dispatcher recorded moments before the shooting. The investigation came after Fox News and others pointed out that the network spliced two parts of the call together, making it appear as if Zimmerman had said, "This guy looks like he's up to no good. He looks black." In reality, Zimmerman was answering a dispatcher's question:

immerman's lawyer, when shown part of the interview being aired Sunday night on Dateline, emphasized that his client would be claiming self-defense.

"I think there were efforts made to render aid to Trayvon," Craig Sonner told NBC's TODAY show.

Mary Cutcher told Dateline that she and her roommate both saw Zimmerman "straddling the body, basically a foot on both sides of Trayvon's body, and his hands pressed on his back."

Cutcher added that Zimmerman told her and her roommate to call the police.

"Zimmerman never turned him over or tried to help him or CPR or anything," Cutcher said.

Sonner also reiterated what he had said in recent days, that Zimmerman suffered a broken nose and a gash to the back of his head.

The FBI, the Justice Department's Civil Rights Division, and the U.S. Attorney's Office for the Middle District of Florida will investigate the killing of Trayvon Martin, an unarmed 17-year-old Florida high school student, who was shot by a self-appointed neighborhood watchman.

"The department will conduct a thorough and independent review of all of the evidence and take appropriate action at the conclusion of the investigation," a statement released by the Justice Department this evening said. "The department also is providing assistance to and cooperating with the state officials in their investigation into the incident."

George Zimmerman, who claimed self-defense in shooting Martin, has not been charged with any crime in the fatal shooting of the teenager on Feb. 26.

Outrage over the incident has only grown, as irregularities in the police investigation have been uncovered and 911 tapes released last week showed Zimmerman ignored a dispatcher's directive not to pursue the teen.

Zimmerman also blatantly violated major principles of the Neighborhood Watch manual, ABC News has learned.

The manual, from the National Neighborhood Watch Program, states: "It should be emphasized to members that they do not possess police powers, and they shall not carry weapons or pursue vehicles. They should also be cautioned to alert police or deputies when encountering strange activity. Members should never confront suspicious persons who could be armed and dangerous."

Yet Zimmerman made a nonemergency call to police and pursued him anyway, even though 911 dispatcher told him not to, before fatally shooting the teenager.

The Sanford, Fla., Police Department, relenting to massive public pressure, released parts of these 911 tapes pertaining to the shooting.

On the tapes, Zimmerman, claiming Martin looked intoxicated, says he saw the teenager cut through from the main street in the tidy Retreat at Twin Lakes, onto a path between two blocks of townhouses, and decided to gave chase. Zimmerman told a police dispatcher, "These a**holes, they always get away"

Dispatcher: "Are you following him?"

Dispatcher: "OK, we don't need you to do that."

Zimmerman didn't stop and ultimately confronted Martin, who was carrying a package of Skittles and a bottle of iced tea. The two allegedly scuffled. In a series of seven 911 calls, eyewitnesses reported that they heard a sort of howling. One caller said, "they're wrestling right in the back of my porch, one man is yelling help."

Then a gun shot rang out. The howling and yelling stopped.

Zimmerman wasn't arrested at the time, and ABC News has learned he was not given a drug or alcohol test that night -- standard in most homicide investigations.