Medical examiners use various methods of determining the approximate time of death of their patients. Approximate time of death can provide a foundation for which to build a timeline of a person’s death. Doing so assists in the investigative process.
1. Livor mortis, or lividity. When a person’s heart stops beating, his or her blood settles to the lowest points of gravity. If he’s laying on his back, the blood will settle in his back, buttocks, back of the neck, etc. Approximately 20 minutes after death, the skin in these areas start to change color as a result of the blood pool. The skin will turn a purplish/pinkish/brownish/reddish (it really varies, especially by skin color). Four to eight hours after death, depending on various factors such as weight, temperature of the room, medical history, medications etc, the lividity will become “fixed” and it will no longer be possible to “move” the lividity by rolling the person over, or by pressing the skin with a finger. When lividity is not set, pressing into the skin with a finger will turn the skin a white color, and then it will turn back. Similar to what happens when you press down on your fingernails.
2. Rigor mortis. This is the infamous stiffening of the joints after death, due to metabolic acid build up. Rigor starts forming between 1-2 hours after death, maximizes at 12 hours after death (complete stiffness), holds for another 12 hours, and then goes away over 12 hours. In short: it lasts 36 hours. The “degree” of rigor, or how stiff the person is, can assist in determining how long the person has been dead. If he or she is in full rigor (there’s no way to move their joints), you will know they have been dead for approximately 12-24 hours.
3. Family statements. The family saying things such as “I last saw him before bed, at X:XX PM” can provide a basis for which to determine approximate time of death.
4. Clues around the house. The state of the house, especially when a person is already decomposed, can provide helpful information.
The following are just a few examples of clues around the house that can assist in the investigation:
a. The decedent has five days worth of mail built up
b. No electricity in the house
c. Dust build up on everyday things, such as the sink, toilet, fridge, etc.
Despite TV shows such as CSI, medical examiners can only estimate time of death; however, new scientific techniques are being invented all the time. Who knows what will happen ten years from now.