DNA Evidence Explained

The attorneys at SQ Attorneys handle a broad range of cases from simple misdemeanor offenses to serious felony matters. DNA (deoxyribonucleic acid) evidence is an important aspect to many serious felony offenses such as murder and/or rape charges. Many have heard of DNA, and may have a basic understanding, but what exactly is DNA?

DNA is the basic building block of life. The information encoded in all organism’s DNA acts as a blueprint for the organism’s biological development and functioning. DNA exists in the cells of all living organisms, and by testing the DNA found in a person’s cell, scientists can come up with a DNA profile for that individual. Only one-tenth of 1 percent of human DNA differs from one individual to the next and, although estimates vary, studies suggest that forensic DNA analysis is roughly 95 percent accurate.

Only until the mid-1980s did DNA profiling of individuals came in to existence. An English scientist by the name of Dr. Alec Jeffrey’s, discovered that certain areas of the DNA strand contain patterns that repeat many times. The number of these repetitions varies between individuals and Dr. Jeffreys developed a test to measure the variation in length of these repetitions. Using this test, Dr. Jeffreys found that he was able to identify individuals by comparing samples of their DNA. This test that Dr. Jeffreys developed became known as restriction fragment length polymorphism (RFLP), which was commonly used in examining DNA evidence in the mid-1980s.

RFLP is an accurate and reliable test, but it requires a relatively large amount of DNA to work. Laboratories now use tests based on the polymerase chain reaction (PCR) method, which allows for testing on very small amounts of DNA from biological samples. Today, a small amount of DNA can be tested through PCR in providing evidence within a crime scene.

Investigators can collect DNA evidence from a number of different sources. Almost any biological evidence can contain DNA, although not every sample contains sufficient amounts of DNA to enable DNA profiling.

Forensic investigators analyze the biological samples to get a DNA profile of the individual(s) that the samples came from. If investigators already have a suspect in mind, they can collect samples to compare to the evidence collected at the scene. There are also databases of DNA profiles that investigators can use to identify suspects by comparing the database information to the DNA profile obtained from the biological evidence.

Assuming that investigators properly collect and handle biological evidence and that the forensic scientists employ accepted methods and conduct the analysis correctly, DNA evidence is extremely accurate. It is a defense attorneys job to carefully analyze and investigate whether or not DNA evidence was properly collected. The chances of one individuals DNA profile matching another persons are extremely small but there continues to be quite a bit of debate about this.

Compared to fingerprinting or eyewitness testimony, which both can be inaccurate, DNA evidence is a highly effective way to match a suspect to biological samples collected during a criminal investigation.

Because of its accuracy, criminal lawyers increasingly rely on DNA evidence to prove a defendants guilt or innocence. DNA evidence has exonerated people through post conviction analysis of biological samples. Since DNA analysis didn’t exist until recently, a reexamination of evidence collected during older investigations can reveal that the DNA profile of the person convicted of the crime does not match the DNA profile from biological samples collected at crime scenes.

Errors in the collection and/or handling of the biological samples used for the DNA analysis can result in the exclusion of DNA evidence at trial. Similarly, if a lab contaminates the biological sample or is found to use unreliable methods, a judge may reject the DNA evidence at trial.

When challenging DNA evidence, defense attorneys will usually focus on the behavior of the investigators and forensic analysts in an attempt to cast doubt on the results of DNA profiles, rather than attack the reliability of DNA profiling as a whole. A well-known example of this is the defense strategy was used in the O.J. Simpson trial.

If you or a loved one is in a bind as a result of a criminal charge, immediately contact a Seattle Criminal Attorney. A Criminal lawyer is not going to judge you, and understands that everyone makes mistakes. Hiring a Seattle Criminal Lawyer to help can – at a minimum – reduce penalties, and can help direct people on how to best deal with their criminal charge, and many times even get them dismissed. So it should go without saying that someone cited for a misdemeanor or felony should hire a qualified Seattle Criminal Lawyer as soon as possible. Criminal charges can cause havoc on a person’s personal and professional life. Anyone charged with a crime in Washington State should immediately seek the assistance of a seasoned Seattle Criminal Lawyer.

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