British filmmaker Nick Broomfield specializes in highly personal documentaries on unsavory subjects. His new "Biggie & Tupac" focuses on two of pop music's greatest tragedies -- the slayings of rap superstars Biggie Smalls and Tupac Shakur -- and manages to render them even more distasteful than they already are. In September 1996, a drive-by shooter in Las Vegas pumped four bullets into the chest of rap and film star Shakur, who died six days later at age 25. Six months later, Smalls, 24, was killed in a drive-by shooting outside an industry party in Los Angeles. He died instantly.

Both shootings occurred amid a highly charged "East Coast-West Coast" feud that pitted Shakur and Death Row Records head Marion "Suge" Knight against Smalls and his ally, Bad Boy Entertainment's Sean "Puffy" Combs. (Combs did not acquire his latest appellation, "P. Diddy," until several years later.)

And both homicides remain unsolved. Police have blamed uncooperative witnesses, but incompetence also may have played a role. A year-long inquiry into Shakur's slaying by a Los Angeles Times reporter contended that "police committed a string of costly missteps" in the investigation. That account, published last month, concluded that members of a Compton street gang known as the Southside Crips killed Shakur and that Smalls had provided the gun and offered to pay $1 million for the hit.

The furor that greeted the article, written by staff writer Chuck Philips, says something about fans' enduring loyalty to Smalls, but it also suggests that many in the hip-hop world would prefer to leave these painful episodes in the past. Talk to a handful of hip-hop fans and you'll probably find people who'll argue that the unsolved killings are a travesty of justice. They wonder whether the results would have been the same if the slain celebrities had been white. Talk a little longer and you'll start to hear myriad theories about what really happened. Like the Kennedy assassination, the hip-hop homicides have given rise to a great deal of speculation and rumor-mongering.

Into this mess comes Broomfield, a bumbling journalist who never met a conspiracy theory he didn't like. (His previous ampersand picture, "Kurt & Courtney," suggested that Kurt Cobain's wife, Courtney Love, may have had the despondent rocker killed because he planned to divorce her; his death has been ruled a suicide.) This time, Broomfield explores the possibility that both Biggie and Tupac were killed by renegade members of the Los Angeles Police Department who were working at the behest of the fearsome Knight.

To that end, viewers are introduced to two former LAPD officers, one of whom was recently jailed for "having a car trunk full of AK-47s." It's hardly inconceivable that some LAPD officers are corrupt, but the vague pronouncements and evasive explanations offered by Broomfield's sources are unconvincing. Shakur's mother, Afeni Shakur, refused to participate in the film, but we do meet his biological father, as well as Biggie's outspoken mother, Voletta Wallace. We also meet a mystifying array of characters, including a man -- currently in jail for "impersonating a lawyer" -- who claims to have played a peripheral role in Small's death, and a woman who enjoyed "orgies" with crooked cops.

This disappointing film contains a few interesting moments, including a young Shakur amusing friends with a Rick James imitation. There's also footage of Smalls's funeral procession through Brooklyn that speaks volumes about the passion behind hip-hop. Then there's Biggie's mother, who seems to believe that hip-hop's regional dispute was behind her son's death. "All it was was a Puffy and Suge Knight war," says the Jamaican-born Wallace. "Hell break loose. So if that's the case, Puffy, Suge Knight, solve your damn problems. They should have done that. . . . Come on now, you're messing with lives here! And that's exactly what happened. Two lives were lost as the result of what? Stupidity?"

Unfortunately, Broomfield's style of journalism is hardly journalism at all, and even those with an avid interest in the subject will grow impatient. We spend lots of time accompanying him as he drives to his interviews, which may explain why he runs out of audiotape during one of them. And when he finally scores a jailhouse one-on-one with Knight (the hip-hop mogul was serving time for a parole violation stemming from a hotel lobby melee that preceded Shakur's slaying by several hours), Broomfield doesn't ask any hard questions.

So Knight rambles on and on without saying much at all -- a fitting end to this futile film.

Biggie & Tupac (107 minutes, at Visions Cinema/Bistro/Lounge) is rated R for explicit language and violence.

The 1990s slayings of hip-hop stars Tupac Shakur, above, and Biggie Smalls have not been solved.