Deceiver is a twisty story. Here's what we know. The end of the film shows Tim Roth dying during an epileptic seizure in the interrogation room. But wait, why did the camera zoom in on the clear bottle of black pills. Those aren't his epilepsy pills... And then the camera zooms in on one of the EMTs. Hey, wait a minute, it's the doorman from Mook's secret gambling den. Then in the funeral home, a man talks to the father of James Wayland (Tim Roth) and says that the body is going to be cremated. But wait, it's another guy from Mook's gambling hall, the guy who tipped Braxton (Chris Penn) about the long shot horse. Now, it's obviously not coincidence that these men appear in key positions in arranging for the disposal of Tim Roth's corpse.
The last scene of the film returns to the park, where in Roth's official police statement claimed to have run into Elizabeth Loftus (Renee Zellweger), a known 'working girl' by chance. This is a prostitution area. Now the film shows the supposedly dead Roth there again, talking to another hooker. And he lights her cigarette with a zippo lighter. Why has Roth faked his own death so elaborately? Hey, wait a minute, whose zippo was that? Could that be Detective Kennesaw's lighter? (Remember the scene where Kennesaw sees that Roth's pupils won't dilate by lighting his cigarette).
So here's some interpretation. Well, it seems to me, that Roth was in love with Zellweger, but not for sex, but deeply emotionally involved with her. His final confession before his seizure was true. He had a fight with his dad. He went to Zellweger's house to console himself, they as he said 'drank the house dry'. He went to by some beer, came back, and someone had just rushed out of the house having strangled Zellweger. In desperation, he cuts the body in half and leaves the pieces in different parts of the city. As he said, the best alibi seemed to make the truth seem so outrageous, it would be ruled out as impossible. So he figures out through the incriminating video tape that Kennesaw murdered his darling hooker with the heart of gold.
The police, in the mean time are chasing up the wrong tree because of the brutality of the crime. (And if you accept Kennesaw as the killer, some willful misdirection on his part.) But Roth sticks to his guns, and repeatedly hammers in that he met the girl in the park. (But don't forget she was an upscale hooker, that used a service, and not likely to be scoring dates in a park.)
So here we have the heart broken Roth, he knows who the killer is but he can't just scream "he did it". Because he is a suspect too. So he presents all his evidence, which probably won't be enough to convict the cop, then conveniently fakes his own death using the pills he gets from Mook that are compared to the ancient Greek mythological River of Lethe, the river which the dead must cross. He then waits a year, returns to his home town, and we must assume, kills the hooker, plants the incriminating lighter on her body and saws the body in half. Tim Roth is dead, yet was assumed to be the killer. So now we have a repeat of the crime, and a quick glance through the case file of the previous murder will show that both girls were met at the park, except now the evidence points to the only suspect alive (as far as the authorities know), good ol' Detective Kennesaw. Braxton will probably admit that Kennesaw destroyed the video tape, but was afraid to turn him in, so instead requested to be transferred. Where did Braxton get the money to pay back Kennesaw before tranferring, anyhow, was he in on it the whole time? Case closed. This may seem elaborate, but think, it is exactly Wayland's (Roth) style, with him saying the more improbable, the better, as far as he's concerned.