What’s a true crime case that haunts you?

Clutter case, "In Cold Blood" murders. Family slaughtered during a home invasion robbery in rural Kansas, after one of the family's farmhands ended up in prison and told a cellmate that the family had a safe with $10,000. They didn't. The robbery netted about $40 and 4 dead people. The killers were hanged, which of course just added to the carnage. (Robert Blake, who played one of the killers in the movie and ended up charged with murdering his own wife, died a few weeks ago.)