There is a strong movement towards building up a national DNA bank to catch criminals.

A human DNA (deoxyribonucleic acid) is the amino acid string that is knitted into the X or Y shaped chromosomes inside the nucleus of a cell.

The DNA string is built like a ladder. Each rung of the ladder is made up of only four amino acids - either the Adenine (A)-Cytosine (C) pair, or the Thymine (T)-Guanine (G) pair.

13 regions of the DNA molecule contain "genetic markers" that can be translated by the scientists into a 52-digit number unique for every human being, unless they are identical and same-gender (monozygotic) twins.

Police officials in the United States have matched such unique DNA markers to the samples collected at the crime scenes to solve 30,000 "cold cases." Currently there are 3 million DNA markers in such databanks and the number of those DNA samples are growing by 80,000 per month.

The civil liberty watchers cry out aloud that the practice violates the Fourth Amendment of the U.S. Constitution: "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."

The critics insist that the automatic scanning of all DNA markers in a genetic databank against the crime evidence, drags an innocent person into a crime investigation even when there is no clear evidence or reason to suspect the individual's involvement.

They claim that the time-honored principle of "innocent until proven guilty" is turned inside out. With automatic DNA scanning everyone becomes "guilty until proven innocent by the DNA test."

The defenders of DNA scanning admit that everyone would be treated as if they are guilty however, if all U.S. citizens do have DNA samples in the database, then no one would be treated differently and everyone would have exactly the same chance of being found guilty.

One big concern that DNA matching brings up is the spreading practice of "familial searches." This happens when the police finds DNA material at the scene of a crime that matches the DNA of a known criminal. Then the police starts investigating his or her family members on the grounds that only those within the same family could have such a similar DNA marker.

Civil liberties critics argue that this new version of "guilt by association" violates individual rights as well.

Five states including Virginia already allow the DNA scanning of people arrested. Even when such people are not indicted, there is a tendency to keep their DNA samples even long after such suspects are exonerated and released. California will also start DNA scans at every arrest by the year 2009.

I think we will hear a lot more about this issue in the years ahead that both promises a strong tool to fight crime in general and raises some serious constitutional issues about the protection of our civil liberties.

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