The criminal needs to realize that there is no coincidence when it comes to murder.
I used to hear a similar comment a lot on the old MSNBC Geraldo show, stated as "We don't believe in coincidences here". But "coincidences" are absolutely inescapable and do not constitute evidence per se. They can of course be a subjective part of a case and give inferences. We are obviously very suspicious of a request to have the victim's sister check for a fax and she "happens" to find the body. But that coincidence, which we find very suspicious, develops only because of the unusual request and questionable behavior of the husband.
Just off the top of my head I can recall a case in Texas in which an innocent black woman went to prison for murder when she coincidentally came to police attention off a motor vehicle registration...she looked like a double for their murder suspect, had the same name (something like Elaine Brown), drove a VW like the suspect, and worked in a fur factory which seemed to link with the fact the victims were fur dealers. She served prison time until the real killer was identified.
Also, the 19 yr old girl murdered in Wyoming and her flashy sports car was missing..old boy friend shows up at funeral...police suspicious and go to his home in another state and find a matching car in his driveway. Surprise! He had bought an identical car, color and all. Fortunately no police entry with guns blazing.
A federal case in California (L.A.) rested on the fact that a Hispanic man and a Chinese woman driving a yellow Cadillac robbed a bank. Just such a couple was found owning a yellow cadillac and they were convicted largely on that basis. It was overturned on appeal when mathematically it was shown that the seemingly damning coincidence mathematically produced a number of such couples in that area of CA.
I write this just to say that mathematics mandates that many, many remarkble coincidences occur in life (and murder cases), and what is obviously true over an aggregate of events must at least be recognized to exist in the individual cases. Coincidences produce suspicions whereas direct evidence suggests a causal connection.