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Bad Lieutenant’s signature image is an unforgettable one: The unnamed Lieutenant himself, played, or rather embodied, by Harvey Keitel, stands nude in a dimly lit New York bedroom, strung out and sobbing, arms raised in grotesque homage to the crucifixion. The image is equal parts mesmerizing and repulsive. Naturally the distributor made it the theatrical poster. Keitel’s wasted, worn-out figure soon became the world’s de facto introduction to Abel Ferrara’s low-budget crime drama, an iconic provocation promising all manner of depravity and debasement.

It isn’t difficult to appreciate why the distributor, eager to leverage the misbehavior indulged in throughout Bad Lieutenant, would seize upon an image of such stupendous vulgarity as the foundation of the film’s marketing campaign — if that’s what they’ll put on the poster, you’re meant to think, just imagine what else the movie has in store? So just how bad does it get? Well, Keitel’s innumerable misdeeds are certainly distressing, at least to the degree that those tempted to the film by the promise of degeneracy will leave duly satisfied. Bad Lieutenant boasts a veritable catalogue of sin: bodies are savaged, young girls are defiled, drugs are variously ingested and injected. In one of the film’s most notorious scenes, the Lieutenant blackmails two women into stripping and simulating oral sex while he stands by masturbating. In another, a nun is violently raped on the altar by a pair of snarling thugs. There’s hardly anything the Lieutenant won’t do — and even less Ferrara won’t show us.

And yet for all its lurid indecency, Bad Lieutenant is hardly an exercise in B-grade exploitation. Ferrara, too, for all the sin he unflinchingly scrutinizes here as in other films, is not an especially flamboyant filmmaker, and if his work at times makes us uncomfortable it’s important to remember that there is a purpose. This misconception is partly a result of pedigree. Ferrara began his career working on the margins of the industry: his first feature, Nine Lives of a Wet Pussy, was very much the low-budget porno it sounds like, put together with pocket change and featuring his girlfriend in the starring role. He made waves with his slightly more legitimate follow up, The Driller Killer, which earned notoriety precisely for the power-tool murders promised by its title, but which also, more significantly, revealed a director more invested in the aesthetics of film than you might expect of a schlock-horror amateur.

It was the arrival of his third film, the unexpectedly artful rape-revenge thriller Ms. 45, that confirmed Ferrara’s seriousness as a developing auteur, and in the thirty-some years since its release it has been reclaimed by critics as a masterpiece of genre filmmaking. What Ms. 45 made clear was that Ferrara’s interest in the profane and the crude was in fact quite high-minded, embraced and studied for what it can tell us about human nature rather than indulged in for the sake of exploitative gratification.

Not that the MPAA took Ferrara’s art into consideration: they assigned Bad Lieutenant an NC-17 rating upon its theatrical debut, resigning it to box office failure. In order to secure its VHS release a more commercially viable R rating — Blockbuster Video rather infamously refusing to stock rental copies of anything NC-17 — the film’s distributor submitted a heavily edited cut. They excised much of what the MPAA had deemed “gratuitous”: glimpses of full-frontal nudity, close-ups of needles in arms, a few snatches of harsh language. In other words the R-rated cut reigned in what, in Ferrara’s conception, had quite deliberately bordered on excess.

But Bad Lieutenant isn’t extreme for its own sake. Its sex and violence aren’t included as empty provocation, or for the titillation of the easily amused. The film has higher aspirations. It is a determined, unblinking look at the world at its worst, a reckoning with what it means to deal and suffer pain, a portrait of a lapsed Catholic groping in the dark of a meaningless life for the promise of redemption.

Ferrara, it’s worth pointing out, isn’t endorsing his Lieutenant’s bad behavior. He isn’t glamorizing drug use, romanticizing violence, or relishing any of this unmitigated excess. He isn’t going out of his way to condemn any of these things either, but that’s part of the bargain of what Ferrara is doing here: He’s simply looking, without judgment or reprisal. Introduced to the film by its misleadingly sensational marketing image, you might go into Bad Lieutenant expecting something racy or obscene. What you get instead is a movie whose style is deliberately flat and unembellished, refusing to trump up the grotesquery happening in just about every scene. When Ferrara shows the Lieutenant shooting heroin in vivid detail for several minutes, the “excess” isn’t meant to be any more exciting, or provocative, or even shocking. The effect is the opposite: the excess renders an appealingly dangerous activity totally, mind-numbingly dull. And what do you think shooting heroin all day is actually like?

It’s not a party. It’s routine.