THE CRIME SCENE
To solve a crime the first 48 hours are fundamental. This theory is now universally accepted and acclaimed. It is for this reason that the crime scene has became, more and more, one of the most important things of the entire investigation. The more correct information are obtained on the crime scene, the more it will be probable to follow the correct track and catch the guilty. Before examine and analyse the crime scene, it is necessary to contact and question the person who launched the alarm and reported the crime to the police. It isn't rare, and the possibility must not be neglected, that this person could be involved in the crime itself. It is important to know who he is, how he discovered the crime, where he lives, with whom and if he knew somehow the victim. Another fundamental precaution to take before concentrating on the crime scene, is to bound it and make sure nobody (strangers, curious or the police itself) can ruin eventual proofs. Many investigations have started and badly ended due to inattentions (so called “contaminations”) caused by the specialists of the crime scene. Honestly this used to happening more often in the passed years, when the less evident traces could not be founded, as it happens today due to very sophisticated technologies. Today the level of attention is higher. Nobody can smoke, par example, on the crime scene or enter it without shoes protections and specific overalls. Only after all these precautions are taken it is possible to access the crime scene. The analysis requires a huge patience, attention and competence. Starting point are photos and videos to be able to re-watch the scene as it was and with all the objects in their exact positions. Now, it is also normal to make surveys with a laser-scanner. Two are the most used: 3D laser scanner and the “time of flight” scanner. The first allows scans of small objects and areas. The second one, instead, allows surveys of larger areas, in the order of approximately one hundred metres, so it results perfect for outdoor scenes where it is possible, during a following analysis, to identify the possible way in and out of the guilty.
THE MOMENT OF DEATH
The first question to give an answer is to establish the moment of death. The coroner is the one in charge of the body and does all the analysis. In front of a body in good conditions he studies the normal physical reactions post-mortem to establish with precision the date and time of death. The principals he can relay on are the algor mortis, the rigor mortis and the livor mortis.
The algor mortis is the reduction in body temperature following death. Many are the surveys done. A first measurement of the temperature is done and then many others to check, each hour, how many degrees the body looses. Starting from this and the initial temperature it is possible to return back and establish with a reasonable precision, the time of death. This is a variable indicator as external factors such as local temperature or the type of dresses on the body can have a significant influence.
The livor mortis is the tendence of the human body, after death, to assume a red discoloration of the skin in the lower portion of the body. In practice, if a body is found positioned face up, red marks will be found on the back (with the exception of the points of support of the body as pression prevents it). At the beginning this phenomenon is not stable. If the body is moved the red marks will tend to desappear and appear in the areas nearer to the points of support. Livor becomes stable after few hours.
The rigor mortis is the stiffening of the muscles after death. Rigor usually sets in about 1 to 3 hours after death. External factors are again very important to establish the velocity of the procedure, but usually 36 hours are enough to complete the phenomenon. Also this can be useful to established if a body has been moved after death or not. A body found in an anomalous position (for example an arm lightly raised) shows without any doubt that it has been moved few hours after death and that probably the place where it was founded is not the same of where he died.
The majority of the murderers is committed by people that the victim knew. This is not the case of the serial killers as they are oriented towards the “category” of preferred victim and they concentrate on this without having to know his prey. In spite of all, also in case of a serial murder, it is very important to know who the victim is, if she matched the target of the killer, if she frequented the same places and any other type of information that can confirm, without any doubt, the link between predatory and prey. If the body is in an advanced state of decomposition and face is difficult to recognise, there are other surveys which can find the identity. These surveys are done in any case by the authorities as an informal recognise can be at the end a mistake. These surveys are the finger prints and DNA analysis. Both can be done on the crime scene. Hands are immediately isolated into plastic bags as they can also contain traces of the killer (for example epithelial tissue underneath nails in case the victim tried to defend herself). Finger prints are detectable also in extreme conditions. With various methods it is possible to take the finger prints on burned or decomposed bodies. DNA is obtainable directly from tissues of the victims such as teeth, bones, hair, saliva etc or from objects of common use such as a tooth brush or cigarettes. Another important thing of the analysis on the victim is the determination of the cause of death. The coroner makes directly this analysis on the crime scene and, observing the body, he first certifies the death and then, if possible, the cause. In any case the autopsy, done afterward, will give absolute certitude and can confirm eventual suspects born on the crime scene. Lesions on the body often “tell” how things went and how death happened. Every single small particular is surveyed: from evident injuries to minimum signs on the skin that can give important indications. For example small red spots on the face or inside the eyeballs are signs of broken blood vessels, a typical reaction to strangling. If this happens with particular violence, signs are visible on the neck. From the ecchymosis on the neck (from which it is also possible to relieve finger prints of the aggressor) to signs left from instruments used for the criminal act (for example the furrow left from a lace, a strap or a rope).