HELYXZION CSI

Catch A Criminal
A crime has been committed. Circumstantial evidence points to three men. Two of the men are brothers; the other man is unrelated. A trace ot the perpetrator's DNA has been found at the scene of the crime.The science of identifying individuals using DNA sequences is very clear, and the probability of scientific error is extremely small. As a result, DNA evidence has been used to help identify perpetrators of crimes and to exonerate innocent people before they become suspects.

The following sections explain the science behind DNA fingerprinting in more detail.

How Can DNA Sequences Identify Individuals?
What Does a Match Mean?
Forensic DNA Evidence
DNA Identifier

Most people share very similar gene sequences, but some regions of DNA sequence have been found to vary from person to person with high frequency. Comparing variation in these regions allows us to answer the question of whether two different DNA samples come from the same person.

The FBI’s forensic DNA identification system probes thirteen such regions in the genome. Sequences in these special regions involve multiple repetitions of short combinations of letters, such as GATA. Easily detectable differences between people lie in the number of repeats that occur in both copies of their DNA in these regions. For example, at one of these regions a person might have inherited four repeats (GATAGATAGATAGATA) from their father and six repeats (GATAGATAGATAGATAGATAGATA) from their mother at the same location in the genome. Another person might inherit eight repeats (GATAGATAGATAGATAGATAGATAGATAGATA) from their father and five repeats (GATAGATAGATAGATAGATA) from their mother.

When two DNA samples match completely in a large number of regions, such as the 13 used in the FBI’s CODIS system, the probability that they could have come from two unrelated people is virtually zero. This fact makes DNA identification extremely reliable.

Injustice Corrected

It takes both sequences at all 13 sites to prove a DNA match, but it only takes one sequence to prove a mismatch. DNA evidence has been used to liberate a growing number of people who were falsely imprisoned for crimes they did not commit.

DNA identification is based on probabilities. Consider the case of just three CODIS sites. The probability that someone would match a random DNA sample at any one site is roughly one in ten (1/10). So the probability that someone would match at three sites would be about one in a thousand: 1/10 x 1/10 x 1/10 = 1/1000 Applying this probability equation to all 13 CODIS sites would mean that the chances of matching a random DNA sample are about one in ten trillion: 1/10 x 1/10 x 1/10 x 1/10 x 1/10 x 1/10 x 1/10 x 1/10 x 1/10 x 1/10 x 1/10 x 1/10 x 1/10 x = 1/10,000,000,000,000 Actual probabilities vary, depending on several factors. But the probability of two different people matching at all 13 CODIS sites is virtually zero.

The science of identifying individuals using DNA sequences is very clear, and the probability of scientific error is extremely small. As a result, DNA evidence has been used to help identify perpetrators of crimes and to exonerate innocent people before they become suspects.

The value of the evidence depends on the quality of the DNA samples and how well law enforcement agencies handle them. Most legal disputes over DNA evidence challenge the handling and storage of DNA samples.

Sources of DNA Evidence

DNA can be left behind in a surprising variety of forms, including saliva, blood, semen, skin, hair, tears, and more. As a result, crime scene evidence can often be traced to a specific individual even if there were no eyewitnesses, and DNA tests provide a more powerful tool than fingerprint analyses.

''COMING SOON"

THE NEXT GENERATION OF THE CSI ANVIL VEIWER WILL INCORPORATE THE ADVANCED TECHNOLOGY OF BEING ABLE TO CREATE A DIGITAL PICTURE OF A PERSON INSIDE AND OUT RIGHT DOWN TO THEIR FINGER PRINTS FROM THEIR DNA ALONE.

THIS TECHNOLOGY WILL BE INVALUABLE FOR IDENTIFICATION AND MEDICAL DIAGNOSTICS!