They might be overwhelmed and flooded by swirling, irrational thoughts, or they might detach and become emotionally numb.
But how soon do they recover, what drives them to switch to relatively rational decision making about where and how they hide a body and how do they get it to a chosen location?
Those are the questions criminologist Nathan Ryan wants to answer.
"There's a lot we don't know about their emotional state in that moment," Dr Ryan told AAP.
"(Concealing remains) can be a gruesome process, but we'd like to know whether they're rational or if they act out of panic."
The Australian Catholic University researcher and lecturer has been awarded a $350,000 National Intelligence Postdoctoral Research Grant to spend two years delving into what goes through murderers' minds when they hide bodies.
Over the course of the project he intends to interview as many convicted murderers in Australia as possible - ideally, 30 - in a bid to create psychological or personality profiles along with associated patterns of decision making.
If the project goes to plan, police will be able to apply those personality profiles to killers and determine whether they are more inclined to have acted rationally or irrationally following their crime.
Dr Ryan hopes his research will ultimately help police narrow down their searches for murder victims' bodies.
"We're looking at is the decision making process that people go through, but (also) the emotional state after the crime and personality factors that may (come into play)," he said.
"What I expect is that people who are less likely to be anxious ... would essentially recover more quickly from the initial shock of their own crime and then engage in more rational decision making."
The project will also look at murderers' knowledge of disposal sites, previous connections with those locations, knowledge of police procedures and the time taken to dump a body.
Dr Ryan in 2019 interviewed almost a dozen homicide detectives about how they pry information from killers to find hidden remains in missing body cases.
In this round of interviews, he will have some of their tactics back-of-mind.
Detectives build rapport with their interview subjects and use "cognitive interview" techniques to bolster killers' recollection and make them feel as though they are back at a scene, Dr Ryan said.
He has built up a resilience against what most would consider distressing conversations but he acknowledges he has to contend with the risk of vicarious trauma.
What drives him is the opportunity to help bring families peace.
"(You read about) the length of time that families have had to endure without being able to find their family member's remains and put them to rest," Dr Ryan said.
"Anything that can increase the probability of finding someone or shorten the length of time it takes to find someone is the bigger goal of this sort of research."
Dr Ryan will collaborate with the Australian Federal Police on the project.
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