If the answer was simple, we wouldn't be here nearly 27 years as puzzled as we are... sometimes you can't keep things simple. Especially with this case.
That’s not strictly true though how much luck was involved in this case?
If Janelle and Mike are innocent and are simply brain dead morons then they screwed up the crime scene so that straight away puts the cops on the back foot. So the crime doesn’t have to be complicated it just needed some luck on their part.