On May 7, 2008, three men robbed a bank in a city called Waldorf of Maryland in the USA. They drove away in a van with a bag of money. They thought they had escaped. But the bank had put a pack of chemicals in the money bag, and the pack exploded. Soon afterward, the police arrested one of the robbers. How did the police find him so quickly? DNA from the robbers' blood was found on the bag of money.
DNA consists of genetic material that is found everywhere in our body, such as in our blood, skin, and saliva. It is our genetic fingerprint. All people have similar DNA, but no two people have the exact same DNA.
The testing works like this: After a crime occurs, the police collect evidence from a crime scene. Some of this evidence may be DNA samples, such as hairs or blood. The database is computerized, and it has millions of DNA samples in it. These DNA fingerprints are taken from people all over the country who have been arrested or convicted of crimes. If the DNA in the evidence matches someone's DNA fingerprint, that person is probably guilty of the crime. But if the evidence does not match, the person is probably innocent.
If DNA evidence is not collected or stored properly, for example, the tests may give wrong results. But it is still more reliable than other types of evidence. Witnesses may identify the wrong person. Lawyers, jurors, judges, and the police can make mistakes. DNA testing is usually accurate.
A. DNA testing is not perfect.
B. The police then set up a DNA database in the country.
C. The robbers dropped the bag, got out of the van, and ran away.
D. The robbers didn't think the chemicals were anything dangerous.
E. How is DNA used to identify a criminal when a crime has been committed?
F. The police then compare this DNA to DNA samples from an official database.
G. It is the best way we have to prove that someone is guilty or innocent of a crime.
