As far as Jennifer Joffe was concerned, the party started the night of Feb. 23, when she let four friends raid the liquor cabinet of her mother’s Boulder, Colo., mansion—and it ended when she stumbled up to bed. But the next morning it was clear that Joffe, 18, had missed some revelry. Mirrors were shattered. Walls were spattered with blood. Police say $40,000 worth of property was gone. And Joffe was certain that she’d been sexually assaulted (Joffe is a pseudonym; NEWSWEEK does not name sexual-assault victims). What she didn’t know, however, was who was responsible for the rampage—and, without other witnesses, neither did Detective Ali Bartley. Until she spotted MySpace.com on Joffe’s PC. “It was like a Pandora’s box,” says Bartley, who spent the next few days monitoring Joffe’s online network of “friends” (and friends of friends) and assembling a “police lineup” of suspects from the portrait photos displayed on their profiles. By March 14, Bartley had arrested six young men—two of the original partygoers, plus four friends they invited over while Joffe slept—in connection with the crimes.

Meet the point-and-click police. A growing number of ordinary officers are working a new beat, turning to MySpace—an online network of individuals linked through personalized home pages—to collect clues and crack offline cases. Communication between cops and the two-year-old company has surged this year, with MySpace now contributing to about 150 investigations a month, according to Jason Feffer, its vice president for operations. That’s due in large part to the site’s size and substance. A searchable, public scrapbook of images, affiliations and written exchanges, it offers detectives raw data on 70 million potential suspects, witnesses or victims (Facebook.com has also served as a source of info, though it is limited to users on college campuses). MySpace has good reason to cooperate with the cops. In the past year, the site has mounted a corporate campaign to counter its growing reputation as a hunting ground for sexual predators—an effort that culminated last week in the hiring of Microsoft’s Hemanshu Nigam, a former federal prosecutor, to oversee security. Today, a 20-member, 24/7 law-enforcement team fields 350 calls a week from its Rolodex of nearly 800 agencies, helping them surf the site and, if necessary, subpoena a suspect’s private messages and registration information. “Criminals are not welcome on MySpace,” says Feffer. “And they will be caught.” (Under Justice Department guidelines, anything posted online is fair game.)

So far, the vast majority of wrongdoers nabbed on MySpace have been the victims of their own hubris. In January, Palmetto Bay, Fla., cops charged a local teen with attempted second-degree murder after members of his “fighting crew” boasted on MySpace message boards of their violent exploits. In March, detectives in Wilkes-Barre, Pa., were able to arrest 10 alleged graffiti artists because they had peppered their profiles with photos of their work. And earlier this month two boys firebombed an abandoned airplane hangar in Novato, Calif.—then uploaded video of themselves committing the crime. (Authorities can also probe profiles for insight into a suspect’s character; on his page, suspected cop-killer Jacob Robida wrote that his favorite “murder weapon” was a hatchet. Robida was killed in a shoot-out with police.) “Users are posting stuff to impress their friends,” says Yahoo! social-media researcher Danah Boyd. “But on MySpace, it’s visible to other audiences—audiences that normally wouldn’t have access.”

As more cops log on, privacy advocates warn that investigative tactics will only get bolder. Detective Rich Wistocki of Naperville, Ill., has two profiles on MySpace: one under his real name (headline: Predator Catcher) and one under a pseudonym. “There’s not a day that goes by that I’m not on there,” he says. Each month, the site helps Wistocki solve three or four cases; he spends the rest of his MySpace time snooping on suspected drug dealers or checking up on local teens. By conducting such surveillance, says Electronic Privacy Information Center senior counsel Chris Hoofnagle, an officer risks crossing “the line between crimes that have been committed and crimes that haven’t. Next he’ll be sucking down information just in case he needs it—and that’s the type of action that upsets a user’s rights.” A company spokesperson says that MySpace will continue to do what it takes to maintain site safety—and that members, so far, have appreciated its efforts. “MySpace is not a police state,” says CEO Chris DeWolfe. Bartley, for one, is unfazed. She’s in the thick of a new MySpace case involving child pornography—and she still browses the profiles of the young men she arrested in March. “Honestly, they’ve had nothing nice to say about me,” she confesses. “But it’s fun to see what the guys are up to.”