Could you maybe cite some French examples where LE has pursued a criminal inquiry in a "missing hiker found deceased" case without a tip that a crime might have taken place?
One case that comes to mind as having some similarities with the disappearance of Esther Dingley is the disappearance of Blake Hartley in Chamonix in 2004. There are many differences too, of course, but the similarities illustrate the protocols followed by the French authorities in a search for a missing person both before and after remains are found.
Blake Hartley was a young officer cadet in the British army who disappeared in Chamonix in the French alps in August 2004 while returning to his campsite after a night out. The story is described in some detail here:
blakehartley.com
Following a period of intense searching using foot patrols, dogs, divers and helicopters, efforts were scaled back until conditions permitted sections of the river below his last known location to be searched more thoroughly with police dogs, divers, and a team of search and rescue police. Sluices and filters were drained and searched. This took place in the winter and spring following his disappearance when water levels were lower. At no point was there evidence of foul play.
In early 2007, a member of the public who had reported seeing a body in the river Arve found a single human femur among debris on a riverbank 60km downstream of Chamonix near Bonneville. At that point a
procureur (a local magistrate) was appointed to conduct an inquiry, and further searches were carried out by police along the sections of river where the remains had been found. Again, there was no evidence of foul play. The remains were identified as belonging to Blake Hartley, and following further investigation, were released to his family in early 2008. The case was then closed by the
procureur of Bonneville. A further inquest was held in the UK in May 2008, and an open verdict was recorded.
I hope this gives a sense of the procedures followed by the French authorities and the timescales involved. The similarities in the case of Esther Dingley are clear. A period of intense searching followed her disappearance. Further searches were carried out as conditions permitted. When remains were found, a
procureur was appointed to conduct the inquiry, and searches resumed to attempt to establish the circumstances and cause of death. None of this suggests any suspicion of foul play, but it's the duty of the
procureur to keep an open mind.