While other people watch reality shows, a marketing specialist in Michigan who goes by the name “Bcclist” spends time in his yard, calculating Trayvon Martin’s last steps with a tape measure and smartphone stop watch.

He is joined on the Internet by Dave Turner, an Illinois man who had his sons yell in the dark from a distance of 30 feet to see whether he could tell which one cried for help.

Both men are often guided by the work of “Tchoupi,” an engineer with a Ph.D. in physics who has spent countless hours making maps, analyzing witness statements and fleeting headlight patterns in surveillance videos to compute George Zimmerman’s moves the night he killed Trayvon.

The three are among a growing group of people on the Internet so fascinated by the mystery of the killing that captivated the nation that they are out to crack the case themselves. They listen to jailhouse calls, pore over witness statements, study evidentiary documents and measure walking speeds.

After hundreds of hours going through the records, some believe they have debunked Zimmerman’s account of what happened that rainy Feb. 26 night in a gated community in Sanford, when the former neighborhood watch volunteer says he was jumped by Trayvon and was forced to kill him during a struggle. Others say the same evidence points a finger at Trayvon, the 17-year-old Miami Gardens high school junior who they believe contributed to his own death. Zimmerman has been charged with second-degree murder.

Experts say the amateur sleuths may very well be the new-media reality for high-profile criminal cases in Florida, where extraordinary public records laws make evidence widely available before trial. In a big case such as this one, prosecutors provide information electronically, meaning anyone with Internet access can comb through the evidence. The bloggers say their intense interest in the case underscores a deep-seated distrust in both law enforcement and the mainstream media, who they blame for shoddy coverage and poor analysis of the facts.

Florida’s “trials of the century” take place so publicly that the exposure of evidence raises profound questions about whether the public’s right to know has trumped a defendant’s constitutional right to a fair trial. With such a serious risk of jury pool contamination, Zimmerman’s attorney jumped into the fray to be sure that the evidence favorable to the defense was reviewed on the blogosphere, too.

Dissing the mainstream media

“The mainstream media overlooked everything,” said Turner, a member of a crime forum called Justice Quest. “Did you really do your job if you didn’t look at the evidence?”

Bcclist listened to hours and hours of car commercials, so he could figure out from the beeping open-door sound recorded in Zimmerman’s call to police what kind of car he drove before that detail became widely known. Criminal defense attorney Jeralyn Merritt, who blogs at TalkLeft.com, seems embarrassed when she admits to spending a recent seven-hour drive listening to the jailhouse recordings of Zimmerman chatting on the phone with his wife and sister. Two citizen journalists in Texas created a site — www.theyalwaysgetaway.com — where they have posted most of the material made available in the case.