DNA Evidence in Criminal Cases: Understanding the Science

In one of the most notorious criminal cases that relied heavily on DNA evidence, the Green River Killer was finally brought to justice after a killing spree that spanned two decades. The Green River Killer, also known as Gary Ridgway, was responsible for the murders of 49 young women in the Seattle area in the ‘80s and ‘90s. The big breakthrough finally came when investigators found tiny paint spheres on some of his very first victims’ bodies that were traced back to the painting factory where he worked. The paint particles were finally analyzed for DNA in 2001, which ultimately led to Ridgway’s arrest and conviction. This landmark case highlights the power of DNA evidence in solving crimes.

Understanding the science behind DNA analysis and its significance can be helpful if you are facing certain criminal charges. As an Orange County criminal defense lawyer, the Law Office of William Bruzzo is very familiar with DNA evidence and is happy to answer any crime-related DNA questions you may have.

What Is DNA?

DNA, or deoxyribonucleic acid, is a molecule that contains the genetic instructions for the development and functioning of all living organisms. It is located in the cells of our bodies and is unique to each creature. Blood, saliva, semen, hair, skin cells, tissue, bone, teeth, urine, sweat and mucus all contain DNA, making it present in items like clothing, personal belongings, and the biological traces one might leave behind at a crime scene. 

DNA profiling, also known as DNA fingerprinting, compares specific regions of an individual’s DNA to identify or exclude them as a potential suspect in a crime. DNA profiling works by comparing specific areas of a person’s genetic material, known as markers, to determine similarities and differences between people. The likelihood of two people having the exact same DNA profile is almost impossible, making DNA evidence a highly reliable tool for identifying people.

How DNA Is Tested in Crime Labs

The analysis of DNA evidence is conducted in specialized crime laboratories. Forensic scientists extract DNA samples from various sources such as blood and skin cells found at a crime scene. These samples are then processed and amplified to create a DNA profile. The profiling process involves identifying specific regions of the DNA that vary between people, known as short tandem repeats (STRs). These regions are amplified using a technique called polymerase chain reaction (PCR), and the resulting DNA fragments are separated and analyzed.

Once the DNA profile is obtained, it can be compared to DNA profiles from crime scenes or other people to establish a match or exclusion. The analysis of DNA evidence in crime labs follows strict protocols and quality control measures to ensure accuracy and reliability.

When Is DNA Evidence Admissible in Court?

DNA evidence can be a powerful tool in criminal trials, but its admissibility in court is subject to certain legal requirements. To be admissible, DNA evidence must meet the following criteria:

• Relevant and Material: The DNA evidence must be relevant to the case and have probative value. It should be directly connected to the crime or the individuals involved.
• Proper Collection and Preservation: The DNA samples must be collected and preserved following established procedures to prevent contamination or degradation. The chain of custody must also be properly documented to ensure the integrity of the evidence.
• Reliable and Accurate Analysis: The methods used to analyze the DNA evidence must be scientifically valid and reliable. The crime lab conducting the analysis should be accredited and follow standardized protocols.
• Expert Testimony: An expert witness, usually a forensic scientist, must testify in court to explain the DNA analysis methods used, the results obtained, and their significance.

Courts carefully evaluate the admissibility of DNA evidence to ensure its reliability and fairness in criminal proceedings.

How Can DNA Be Legally Obtained from Crime Suspects?

Obtaining DNA evidence from crime suspects is a delicate process that involves strict adherence to legal and constitutional rights. In general, law enforcement can collect DNA from suspects under the following circumstances:

• Consent: If a suspect voluntarily agrees to provide a DNA sample, law enforcement can collect it without a warrant.
• Arrest: When a suspect is lawfully arrested, their DNA can be collected as part of the standard booking process. This includes DNA swabs of the inner cheek, which are non-invasive and do not require a warrant.
• Search Warrant: If law enforcement has probable cause to believe that a suspect’s DNA will provide evidence of a crime, they can obtain a search warrant to collect DNA samples.

Talk to a reputable Orange County criminal defense attorney if you have concerns about the legality of DNA collection in your case.

Is There a DNA Database for Criminal Justice?

Yes, there are various DNA databases in the criminal justice system that store DNA profiles for comparison purposes. The most prominent database in the United States is the Combined DNA Index System (CODIS), which is managed by the Federal Bureau of Investigation (FBI). CODIS contains DNA profiles from convicted offenders, as well as DNA evidence from crime scenes.

The DNA profiles stored in CODIS can be searched against other profiles to identify potential matches or connections between crimes. This powerful tool has been instrumental in solving cold cases and linking serial offenders to multiple crimes. However, access to the CODIS database is restricted and subject to strict regulations to protect individual privacy rights.

DNA FAQs for Criminal Suspects

• How long can DNA evidence be stored? DNA evidence can be stored indefinitely if properly preserved. Advances in DNA analysis techniques have made it possible to obtain usable DNA profiles even from very old samples.
• What if there is not enough DNA for analysis? With advancements in DNA technology, smaller and degraded DNA samples can still yield usable results. However, the amount and quality of DNA can impact the reliability of the analysis.
• Can familial DNA searching be used? Familial DNA searching involves comparing crime scene DNA to profiles in the DNA database to identify potential relatives of the perpetrator. While controversial, some jurisdictions allow familial DNA searching in certain circumstances.

Ask an Orange County Criminal Defense Attorney

When it comes to navigating the use of DNA evidence in criminal cases, you may need some trustworthy and reliable legal advice. Set up a free legal consultation today to get started. The guidance of a skilled Orange County criminal defense attorney can be invaluable. The Law Office of William Bruzzo is eager to inform you of your rights and legal options. Reach out now!