The crime scene DNA analysis might be used to determine a suspect's age and whether or not they have cancer. For forensic specialists, a drop of blood left by a suspect at a crime scene is a gold mine. And, in the near future, scientists may be able to learn more about an offender's DNA, including their age. Blood contains genetic information that can be used to identify people who have inherited certain traits from their parents. These include characteristics like hair color, eye color, stature, and susceptibility to disease. In addition, some diseases are known based on changes or mutations in specific genes. One such disease is sickle cell anemia. This condition causes red blood cells to become "sickled" or deformed, which leads to pain episodes and death. Another is beta-thalassemia, which results in poor production of red blood cells and can cause severe anemia.
People who love each other should never find out what happens at a crime scene. If someone tells you that they found out something bad about someone else from looking at their blood at the crime scene, then they were probably lying. Police should never ask you to do this. It is not standard procedure and could prejudice any potential prosecutions.
Blood samples are taken from victims at the scene by crime lab personnel and also from suspects after they have been arrested. Both the location and type of injury as well as how much blood is lost help investigators determine what kind of weapon was used.
Genetic information taken from such biological samples may be compared to DNA databases, for example, to discover if a sample's DNA sequence matches any known criminals. Blood also provides an easy way to identify someone who has no other identifying marks, such as tattoos or scars. Finally, blood contains cells that can be used to study their contents not only in criminal cases but also for medical research.
Blood types are the most common means by which forensic scientists identify people. Each person's blood contains antibodies that react with substances found in different types of blood. These antibodies are called antigens. The blood antigen-antibody reaction occurs when someone was given a blood transfusion or got cut by a knife that had been previously stuck into a banana. The FBI uses blood groups to identify suspects in crimes.
DNA profiling uses the unique genetic code in each cell to identify people. Forensic scientists use DNA evidence to solve crimes and perform human genome research. The DNA profile of every living organism is made up of two sets of chromosomes: one from each parent. Each chromosome has three billion chemical "letters" (base pairs) that are arranged in a pattern unique to each individual. These patterns are called alleles. The two alleles of each gene are called loci. A person's DNA profile consists of the patterns of these alleles at each locus.
DNA is routinely discovered at crime sites during police investigations, and persons of interest may be requested to voluntarily supply a DNA sample. Once a sample is obtained, forensic experts extract and replicate the DNA from cells in body fluids or tissues. The DNA is then analyzed by polymerase chain reactions (PCR) and other techniques to match it with DNA samples from individuals in law enforcement databases, such as CODIS. If there is a match, this information can be used to identify or exclude suspects.
In addition to identifying suspects, DNA evidence has been used to link crimes together and help solve cases. For example, DNA evidence has been used to connect victims and their families with arrests and convictions. DNA evidence has also helped identify the source of some outbreaks of disease - including one case where a man's saliva was used to identify his unknown killer. Finally, DNA evidence has been used to help exonerate people who have been wrongfully convicted of crimes they did not commit.
The ability to use DNA to identify suspects and connect crimes together is being enhanced by advances in technology. For example, computer programs are now available that analyze DNA data sets for similarities. These programs can search through databases of DNA profiles looking for matches with other crimes. When a match is found, the computers generate extensive reports listing the possible related cases.