Understanding DNA Evidence in Criminal Cases

Blischak Law October 10, 2023 Blog,Felony

DNA evidence has revolutionized the way crimes are solved, allowing individuals spending many years in prison for acts they did not commit finally to go free. DNA is the most reliable evidence in any case because everyone has a DNA sequence, differentiating them from others. There is no mistaking someone because of looks, how they dress, or because they were near an area where a crime happened when using DNA as evidence.

But this does not mean that DNA evidence is without fallacy. Several individuals’ DNA samples collected from the same place can contaminate the individual DNA of a person, making it impossible to pinpoint one person in connection with a crime. However, the accuracy of DNA is undeniable and worth understanding when it is applied to cases and Phoenix criminal defense.

Gathering DNA as Evidence

Biological material is taken from an individual as a sample and analyzed in a lab where it can be compared to the samples of others who have had their DNA collected. This material does not have to come directly from an individual but can be taken at the crime scene, making it imperative that contamination does not occur. DNA evidence can be collected from the following:

  • Blood
  • Fingerprints
  • Bodily fluids, including urine, semen, and saliva
  • Skin cells, including hair

From the DNA samples collected, copies of DNA sequences are replicated and then compared to a database containing the samples of other individuals previously collected. There can only be one match to this sample, except for when comparing the DNA of identical twins.

DNA Profiling

With the discovery of DNA as evidence in cases, law enforcement is now able to gather this material at a crime scene and compare the information with a national database of DNA samples known as the Combined DNA Index System(CODIS), making it possible to identify individuals present at some point at a location. Individuals suspected of committing a crime may be required through a court order to supply their DNA to determine if it matches evidence found at a crime scene.

Evidence is divided into two groups known as class evidence or individual evidence. Class evidence belongs to a group of subjects or objects, such as a blood type. But, individual evidence belongs only to one subject or object in a group, and this is the importance of DNA.

DNA’s Limitations

Even though it is the most accurate identifier at a crime scene, DNA still has its limitations, as mentioned previously, and cannot address the vital information below, making forensic expert witnesses invaluable during a criminal case. The accuracy of DNA is not in question. Human error becomes a factor in most cases when using DNA as evidence.

  • DNA cannot determine consent in cases of sexual assault
  • DNA does not identify how biological material was left on evidence
  • DNA cannot place an individual at a place at a specific time
  • Without enough samples to compare with, DNA can produce incomplete profiles
  • Complex mixtures may not be interpretable

There are vital, factual arguments that can be used against DNA as evidence in a crime.

Phoenix Criminal Defense Attorneys and the Use of DNA

Understanding DNA as evidence in a criminal case, from how it is collected to the questions it cannot answer about a crime, can be the difference in a defendant being falsely accused or exonerated. Extracting from years of service and relationships with law enforcement in the Phoenix area, Blischak Law Firm is dedicated to effectively working for clients to protect their best interests. Contact us for a free consultation, and let us provide the diligent representation you need today.