Forensic Search Dogs are specially trained to locate blood and/or semen and can assist other more recognised techniques in the search for vital evidence at the scene of a crime. These dogs are especially effective when the actual scene is not known as they can quickly eliminate innocent areas.
At present the only effective way to locate blood residue is by the use of Luminol. The Crime Scene Investigator (CSI) sprays the area to be searched with Luminol. This reacts with the haemoglobin in the blood to cause a reaction known as chemiluminescence. In short, this reaction causes the blood residue to glow when ultra violet light is shone on it. In order to achieve this effect the area must be completely blacked out.
This process has several drawbacks, firstly the CSI has to spray the correct area thoroughly and then the residue must be within line of sight of the operator. In addition the fact the area has to be in complete darkness excludes exterior searches. The whole process is costly in terms of time and expense. Luminol also has other limitations in that it can destroy other vital evidence and innocent substances, such as household bleach can give “false positives”.
In this respect a specially trained dog provides the solution. Because the dog searches an area three dimensionally and only targets a specific scent it is able to eliminate “false positive” indications
The search for semen presents the CSI with the same problems as the search for blood. At present semen is detected by using “black light”. Semen contains a phosphorus element which glows when subjected to “black light”. This is the same principle as a white shirt glowing in a disco. However, like with blood, other innocent substances such as a highlighter pen mark, also give the same reaction.
The use of trained dogs provides the investigator with the ultimate search tool. Dogs are able to search any area, interior or exterior (not available using existing search methods) and are able to provide pinpoint accuracy thus enabling the CSI to use their skills in recovering the samples.
• Dogs search “3 dimensionally” whereas humans only search “2 dimensionally” i.e. in line of sight
• Dogs are able to discriminate between the target scent and other similar innocent scents
• Forensic Search Dogs are in demand (Madeline and Jersey cases) although very few police forces possess them. Thus making them in demand
• Forensic Search Dogs can be mutli-tasked i.e. One dog can be trained to locate
• Dogs DNA (canine DNA) does not react with human DNA (simian DNA) therefore it is difficult for a dog to spoil any evidence
• Dogs can detect evidence on clothing very quickly. As such they are able to eliminate innocent articles of clothing. This process costs on average £200 per item of clothing in the UK
• Dogs can be used to search a variety of terrains including vehicles
• Dogs can also be trained to locate human remains on land and in water. This extends their usage thus making them even more cost effective. They can be used in crime scenes, disasters (natural) and post terrorist activities
• Once trained, the upkeep of a dog is very minimal