You are right. It is actually more likely the murderer is dead than not. This is a simple observation because lots of people associated with the investigation are dead too. Simply beacause time has passed. Christer Pettersson is dead. Hans Holmér is dead. Lisbeth Palme is dead. 33-åringen is dead. Claes Zeime is dead. Axel Morath is dead. Lars Tingström is dead. Skandiamannen is dead. Ebbe Carlsson is dead. And so on, and so on..