The case of Janet Harvey, a British woman who was found dead in St Paul’s Bay was not a difficult one for investigators to establish how long she had been dead, because there was the testimony of her husband. However, in other cases, forensic science is crucial to establish certain facts about the cause of death. TVM asked forensic expert Dr Mario Scerri what experts look for to establish how long a person has been dead.
While he made it clear that he was not referring to any specific case which is in Court, Dr Scerri explained that when a person dies the muscles start becoming stiff in a process known as ‘rigor mortis’ and according to how stiff the muscles are, one can determine how long the person has been dead. Apart from this, they also observe the colour of the corpse.
“When a person has been dead up to an hour or an hour and a half, you start getting rigor mortis in the small facial muscles and the fingers. This starts to spread until, after three hours, it forms in all the muscles, the corpse continues to become stiffer and after two days this goes away in the same way it came. In other words, if you find a corpse which is semi-flaccid or flaccid, you can say that the person has been dead two or three days. The hypostasis (accumulation of fluid or blood in lower parts of the body) goes through another process and after just ten hours it becomes fixed. There we can have another idea of whether the corpse has been static for more than ten hours.”
Dr Scerri said that the body temperature can also indicate with a certain exactness how long the person has been dead, although various other factors can make a difference.
“Rigor mortis forms more quickly in a people who are heavier because they retain more heat, while in people who are debilitated, cachexia, in other words, those suffering from a terminal illness such as cancer and have muscle wastage, and are very thin, it forms less quickly.”
When a person has been dead for a long time, experts consider other factors including the place where the corpse was found because if it was exposed to the elements, the process of decomposition occurs more quickly.
“Other important factors are the formation of eggs from flies or maggots which can cause complete devastation, and there is even a science, anthropology, which studies the lifecycle of maggots, so from that you can also get clear ideas about approximately how long the person has been dead.”
He added that corpses which are lifted out of the sea usually have a white film, like wax, which protects the corpse and corpses which have been in the heat form what is known as ‘mummification’. Dr Scerri said that the rate of decomposition is also affected by the person’s state of health. He explained that in people who were taking pills and have retained a lot of water, or those who are heavy, the rate of decomposition is quicker than in those who are thin. Dr Scerri said that after two or three days the most, the corpse’s organs also give important signs to forensic science to determine certain facts about the corpse.
Watch the full interview with forensice expert to Dr Mario Scerri here: