Despite the lack of a body, they seem to have Reiser dead to rights. He took the passenger seat out of his car and hosed out the interior right after his wife turned up missing. He seems surprised that investigators found that a bit suspicious.
Reiser's previous defense was that this is all a setup perpetrated by the Russian mafiya. If half of what I've read about the Russian mafiya is true, if they had a problem with Reiser, there would be pieces of him strewn from San Mateo to Concord; they don't seem to particularly keen on arcane frame-up jobs for dealing with schmucks.
Anyway, the platypus defense. And you thought "if it doesn't fit, you must acquit" was a bold gambit.