Usually in cold cases like this, the person of interest is well known to the police but the police do not have sufficient evidence for an arrest. And the case just lies collecting dust. They will allow the general public to speculate in far off fields and on the most unlikely suspects all the while keeping quiet and the lid on what they know until sufficient evidence is revealed for an arrest. There are reasons why the police do this. The police may release what they know after the person of interest dies or after 100 years which ever happens first. I believe the person of interest for the police has been discussed here. Here is a task: rank order all the person's of interest using criteria (i.e. last person to see her alive, male gender, age, Motive:  ) and see who are in the top.