According to statistics by the Federal Bureau of Investigation (FBI), the probability that two Caucasians who are not related but have identical DNA fingerprints is “approximately 1 in 575 trillion.” This tiny number encompasses “pairs” of people. If there are 100 million people in a sample, the corresponding number of pairs balloons to 5,000 trillion. Eight to nine pairs will have matching profiles. Hence, DNA fingerprinting is a complex process founded on probability. A “match” still does not lead to definitive proof that both DNA profiles are of the same person.
DNA profiles furnish insights into an individual’s family relationships, predisposition to diseases and ethnic or racial origins. The information can be exploited by various institutions—insurance companies, banks, schools, government agencies, places of employment, etc.—and could open the doors to genetic discrimination. Law enforcement agencies and forensic services can also access a profile in a DNA database without the individual’s consent.
Once DNA is collected and stored, several states do not require the removal of a DNA profile from a law enforcement database even when suspects have been cleared or a conviction has been overturned. In England, suspects under arrest can be forced to take a DNA test regardless of the severity of the charge. Once an individual’s genome is on file, he can be identified as a match to DNA evidence from a crime scene. Storing the DNA profiles of innocent people presents an array of ethical and social considerations.
The DNA database may only increase the ethnic bias that already plagues the system. When individuals of an ethnic group are more frequently arrested and convicted of crimes, their disproportionately large number will be reflected in the database. There is concern that racial profiling can lead to even more arrests within particular minorities.
More than half a million DNA samples has yet to be entered into the Combined DNA Index System (CODIS), the FBI’s DNA database. For several cases in this massive backlog, the statute of limitations has already expired and the genetic evidence can’t be used.
Often the DNA from a crime scene is either a miniscule sample or too degraded to provide a full profile in a 13-STR test. If so, only a partial DNA fingerprint is possible. The chances of a random match increase. In addition, contamination of DNA can occur at the crime scene as well as en route to and in the testing laboratory.