Juste Avant la Nuit nas never, to my knowledge, been released on either video or DVD in the UK before. It's here now though, on a basic (no extras) DVD and is well worth buying.
Rather than being a murder mystery or detective thriller, it is about a man who accidentally kills, can't cope with his guilt, eventually confesses, and is surprised to learn that his discreetly charming bourgeoisie wife and best friend don't really care that much. So much for the plot - the real wonders of this film lie in its sheer aesthetic beauty - from the elegance of the camera movements, to the brilliant score (if only it was available on CD) by Pierre Jansen, to the perfectly pitched performances. The last 15 minutes or so are deeply strange and also quite moving.
Overall, this is a forgotten gem of French cinema by a great director at the peak of his powers. Most of Chabrol's work from 1968-1975 is comparable with any of the better known auteurs who are idolised today, and this one is strongly recommended.