Legal Guide

What is DNA used for in California criminal cases?

If you have ever watched a crime procedural show on the TV you have probably heard about the use of DNA evidence to help secure a conviction in a criminal case. The actual use of DNA in real criminal investigations and trials is a little different to what you may see on screen. For one thing, the results of DNA testing do not come through in a few hours; just in time to catch the bad guy, before he commits another crime. The process takes more time than that.

It's also important to remember that DNA test results are not always the iron clad conviction tool they appear to be, in works of fiction. We are going to take a look at the details of DNA testing. We are also going to discuss why it's not always completely reliable.

What happens during DNA testing?

Strands of DNA are present in every cell of living things. The DNA that we have in our body helps to determine who we are, including what color eyes and hair we have. When DNA testing is carried out, only part of the strand is tested. This part is called the STR (Short Tandem Repeat) section. It's the part that has the most variety between people. The test involves checking what allele is present on a locus. The test is carried out across 18 to 19 loci. The test establishes whether a DNA sample which was collected at a crime scene matches a DNA sample that was obtained from a suspect.

Why might DNA evidence be called into question?

The problem with DNA testing is that it's not always accurate. Any issues with the collection or testing of DNA can lead to erroneous results. For instance, whoever collected the DNA from the crime scene may not have followed procedures. There may also have been problems with the chain of custody for the DNA sample. There is plenty of opportunity for mistakes to be made when it comes to collecting and testing DNA. This is why a San Diego criminal lawyer may argue against the legitimacy of DNA evidence, in a California court. If they can prove there have been issues with the testing process, the evidence could be prohibited from use in a trial.

You can see that the use of DNA during a criminal case is not as it seems on the TV. Obviously, the process needs to be speeded up, so that crimes can be resolved in forty minutes. The depiction of the use of DNA evidence is based on truth, but it tends to suggest that the results of DNA testing can be 100% relied on. This is not the case, outside of the world of TV.

DNA evidence can certainly be useful in helping to secure a criminal conviction. It can also present significant problems, if the defense can prove that there was a issue with the collection or testing process.

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