YOu seem well versed in forensics. Tell me, what does "D and A" stand for again?
Dainty things never shrink from Lux!

Since Henry was only suspected (hence to title) they could not take samples of his DNA without his permission, so whatever was found on the victims meant nothing without a sample to match it with.

• Don't tease me about my hobbies, I don't tease you about being an assh*le.

MORE SPOILERS
Yes, forensics
were
mentioned. You must have missed that. Henry brings it up when he says there must be testsbodily fluids, DNA, etc (I assume you mean DNA when you say D and A ? Perhaps that was the mumbled bit ?). We hear that both the killer and Henry use condoms, and if you want the gory details chemical lubricants were found in the victims. Victor goes into some detail about the forensic tests at this point. This is why he wants to get hold of the clothes Henry was wearing the previous day.
As I said before, there was no solid evidence, only circumstantial, that Henry could be the murderer. Although Victor would like to net a rich, high-powered attorney, he and Henry go back a long way, and some time is taken to establish that in the film. Victor is exercising
some
caution in how he proceeds, while trying to get Henry to spill the beans. The Owens character is the hothead, whereas Victor is a little more measured. And Victor DOES get Chantals consent to search the house without having to get a search warrant. At this stage, Victor wouldnt want to storm the house without consent, as they are acquainted, even though he appears never to have visited the house. (He uses her too, as he isnt entirely honest about his lack of knowledge of the Camille incident, getting the story out of her through the implication that Henry has talked about it he plays husband and wife off against each other). Also the superintendant asks Victor if he has evidence, and Victor can only say hes caught Henry in a number of lies. The boss is aware of Henrys social status, and you dont mess with that unless youre sure.
I dont know what you mean by
ridiculous
photographic coincidences. Could you expand on that ? The story is stuffed full of coincidences, isnt that the point ? Henrys a photographer, why is that ridiculous ? You say the whole story was so far fetched can you be more specific ?
If you havent read it, you might enjoy the original story Brainwash by John Wainwright, on which this is strongly based, but the Victor and Henry characters in that had never met so the banter is not quite so much on a two-way personal basis, theres a sergeant who beats up the suspect (a sort of Owens who goes too far), and a rather more emotional wife. But the gist of the story is the same they get it wrong,
because
of coincidences. Incidentally, the author had been a policeman.
This isnt CSI where crimes are always solved neatly for our satisfaction..thats not life, at least, not all the time.
Nobodys winning. One sides just losing slower than the other.

Forensics were never mentioned. This story unfolded as if modern forensics had yet to be invented. Henry was not even asked to submit a D AND A test nor finger prints. As for the search, warrant or not that place would have been turned upside down. The whole story was so far fetched not to mention the ridiculous photographic coincidences.

Dont know about the mumbled bit where was that ?
CONTAINS SPOILERS
When Victor asks Henry to go to the police station to clarify his statement there is no solid evidence to link Henry to the crimes. There are, however, things that Victor knows about Henry that we dont know till much later. Victor is a little more reined in with his early suspicions than Owens, who presumably DOES know what Victor knows, which is that Henry was in La Perla and had been visiting hookers for months. All this is circumstantial, but Henry doesnt help his cause by lying, more than once, about what he was actually doing on the night the first girl was murdered. This is on top of his early genuine memory failing about the dog on the previous day, at least I believe this was a genuine mistake. He had forgotten he met Tango during his run, rather than having collected him from his owner. We have to remember, with hindsight, that the later real lies make it look as if hes been lying from the start, in the minds of Victor and Owens. But Henry has no cause to lie at first. Hes innocent of the crimes hes being questioned about. Its only when his aspects of his personal life are being questioned that he lies.
So certainly all the forensic tests will be done on the victims, but you cant take samples from an accused until you have one. Remember this film takes place over just a few hours. Victor, in almost an act of desperation, detains Henry on suspicion, which I dont think is quite the same as being arrested and charged. A search warrant, of Chantals house (remember its a gift), would have come later if she hadnt eventually given her permission, and that was only in response to Victors Dont you want to know if youre right ?.
Please remember this is not a conventional whodunnit. We learn things along with the main characters as the film progresses. Its a case of who knows what, and how much, when. Its about perception, suspicion and jealousy, and there is never any more than circumstantial evidence. Victor is bright enough to know that, but Henrys lies lead him, and Chantal, to a wrong conclusion.
It bombed because it was pulled from theatres after a very short and limited release. I dont know the reasons for that.
Nobodys winning. One sides just losing slower than the other.