Sherlock, St Louis & Co. The Under of Investigation - Cathie Louvet's Chronicle - DNA



Cathie Louvet's chronicle


 Sherlock, St Louis & Co. The Under of Investigation - Cathie Louvet's Chronicle - DNA
 Sherlock, St Louis & Co. The Under of Investigation - Cathie Louvet's Chronicle - DNA
 Sherlock, St Louis & Co. The Under of Investigation - Cathie Louvet's Chronicle - DNA
 Sherlock, St Louis & Co. The Under of Investigation - Cathie Louvet's Chronicle - DNA
Folder n°7: the medical examiner

A corpse has just been discovered: Who is it? How is this person dead? To answer these questions, investigators often need a forensic pathologist, a specialist who works in the service of justice and intervenes in cases of suspicious death.


Temperature: in good health, the human body maintains a temperature of about 37 °. After death, he loses an average of 1 ° per hour and reaches the temperature of his environment in about 24 hours. Thus, to evaluate the death of death, the medical examiner measures the temperature in the rectum, sometimes the liver, using a probe. It takes into account the ambient temperature, body build and clothing of the victim, a possible hypothermia (internal drop in body temperature) due to drowning, for example. It is thanks to all this information that he can give an estimate of the time of death.
Opacification: the cornea is the upper layer of the eye, normally transparent. In a corpse, because of dehydration, it becomes gradually cloudy: it is the opacification of the cornea that allows the medical examiner to have a first clue as to the moment of death. When the eyes are open, this occurs approximately after 45 minutes, and more than 24 hours if the eyes are closed.
Stiffness: some chemical reactions are no longer in the muscles after death, they lose their elasticity. Those of the eyelids and the jaw are the first to freeze in one to three hours, then they are trunk and limbs, to reach a maximum 12 approximately after the death. After 2 or 3 days, this rigidity fades. But since this phenomenon is not measurable because it varies a lot according to individuals and / or external conditions, it is an unreliable index.
Lividity: due to gravity, blood accumulates towards the lowest points of the body that are not compressed to form purplish-red spots: these are cadaverous lividities. They appear a few hours after the death but disappear or change location if the body is moved. After 8 to 12 hours, they become fixed and permanent. Some skin colorings, cherry red for example, evoke carbon monoxide poisoning or cyanide poisoning.

2. Observe:

The autopsy takes place as quickly as possible before the body is degraded. The first step is the observation in which the medical examiner seeks to gather as much information as possible; it must proceed fairly quickly because some clues may disappear over time or during dissection. Often, he conducts a complete examination of the body X-rays before the autopsy in order to visualize possible bone fractures, projectiles to know their trajectory, or indices such as the dentition, the wearing of a prosthesis allowing to identify more easily the corpse.
The autopsy can now begin: the doctor is assisted by a technician called "mortuary". The body is undressed, washed and then lying on a table under powerful lighting. If the identity of the person is unknown, all particular details are noted: tattoos, scars ... The wounds are photographed and described. They can of different nature:
Traces of links: if the victim has been tied or strangled, traces of rope or cable are visible. With a softer cord, the marks are more discreet and will appear more easily during dissection in the deep layers of the skin. Depending on the condition of the skin, the coroner can determine if the bonds were placed before or after death.
Hematoma: during a shock on the skin, micro-blood vessels burst: blood escapes and creates a hematoma whose shape provides information on the object that is at the origin: fist, baton ... Sa color evolves in time even after death, but this evolution is so variable from one person to another that it does not constitute a reliable index.
Impacts of rifle cartridges: they are very recognizable because a shotgun, unlike other weapons, fires a volley of shots. Depending on the distance, the injuries inflicted by shots are not the same: large and unique for a close-range shot, or small and multiple if the shooter was several meters from the victim, which makes it possible to differentiate between a hunting accident and a voluntary shooting.
Bullet impacts: the details of a gunshot wound are a mine of information: is it an entry or exit hole? Was the shot fired at close range (weapon against the skin), at close range (weapon a few inches) or farther away? Was the victim already dead when she received this bullet? Clues that can identify a homicide camouflaged as suicide.
Stabbing: the size of a stab wound and its depth tell the type of knife used (double or single edge), the length of the blade, etc ... The angle and the trajectory in the body can possibly provide information on the aggressor's corpulence and whether he is left-handed or right-handed.
Wrestling Marks: If bruises or sores are visible in the victim's hands or forearms, this suggests that she has defended herself. It may also happen that there are skin residues under the victim's fingernails, residues that will be subjected to DNA analysis.

3. Dissect:

After practicing a large opening in the chest (often Y-shaped), the forensic removes each organ as gently as possible so as not to damage them, for the purpose of studying them thoroughly, because no clue should be forgotten! He begins by observing their outward appearance in case they present wounds. They are then weighed and dissected one after the other: their contents are studied, there is evidence of internal lesions, then samples are taken to send them to the laboratory for further examinations. Everything is absolutely carefully noted!
Equipment: the same outfit used by a surgeon, to which is added a mask, a hat and surgical gloves; the forensic scientist and his assistant must be protected from any risk of contamination in case the corpse carries a contagious disease. Indeed, even dead, a person can harbor bacteria or viruses still active. Sometimes one or more members of the police may attend such an autopsy, but only as observers.
The tools:
A scalpel: makes it possible to incise the skin and to dissect the organs and the soft tissues.
A costotome (or bone clamp): serves to cut the ribs to facilitate the opening of the thorax.
A hand saw and a circular saw: used to cut large diameter bones (eg femur) and to open the cranial box.
A knife: used to cut the organs in thin slices, like the brain or the lungs, to study them under a microscope.
In detail:
Heart and lungs: the heart is carefully scrutinized: did the person suffer from a particular illness that could explain his sudden death? The lungs may also provide important information in the case of suspected accidental respiratory poisoning or, on the contrary, choking by a third party. And in case of drowning, they contain clues as to where it happened (microorganisms, vase).
Digestive organs: the esophagus, stomach, liver and intestines are closely examined for evidence of possible disease. Their content can provide information on the last meal of the victim to trace his schedule in the last hours that preceded his death. Samples are taken in order to carry out additional analyzes.
The cranial box: the forensic relieves the skin of the face and scalp, then cuts the cranial bone with the help of an electric saw to access the brain which will be weighed and then sliced ​​to visualize bleeding or blood clot, which would mean that the person was beaten severely, possibly causing the death.

4. Analyze and conclude:

Once the autopsy is complete, the doctor's assistant puts all the organs back in place and then closes the body, trying to leave as few traces as possible.
Then, a very important step: the writing of the autopsy report. Everything is recorded: the observations of the medical examiner and the conclusions he can draw about the causes of death. It is sometimes much more difficult for him to pronounce on the circumstances: accident, suicide or murder. It also records the results of the tests that the lab has conducted: genetic, blood, poison research.
The report should be written in clear and understandable language by people who are not doctors. Especially since it can be used as evidence during a trial. In 10% of the autopsied cases, the circumstances of the death remain indeterminate, leaving doubt about a possible homicide. It is then up to the investigators to continue their investigations ...

Cathie Louvet