Murder and Rape of young boy

[Hazel]

Hi
I wonder if anyone can help. I cant remember the title or the author but the plot is about a detective investigating the rape and murder of a young boy. As years pass the case is unsolved and the detective begins a relationship with the mother. The rapist kept the boy in the boot of his car after raping him and killed him after going for lunch, I think he bashed the boys head in with a rock. Later on I believe he is some sort of politician and gets caught after shooting the boys mother. I think its set in France.
I know its not much, but would be grateful if anyone could help.

Thank you

[Elizabeth]

Innocent Blood

Possible, but I'll admit, not likely. Includes the elements: rape and murder of young boy, case unsolved for years, relationship with (actually the sister here), rapist keeping the body in the car boot and going to lunch.

[Lobstergirl, au gratin]

Hazel, are you still looking for this or did you find it?