Our attorneys understand the science behind DNA evidence and know how to challenge it effectively. Don’t let flawed forensics determine your future.
DNA evidence has become one of the most powerful tools in criminal prosecution, but it is far from infallible. Contamination, degradation, transfer and laboratory errors can all lead to misleading results. At Birkholz Law, our criminal defense team includes attorneys with specialized knowledge of forensic DNA evidence and how to challenge it effectively.
Our firm works with qualified DNA and forensic experts as needed to review, analyze and challenge the prosecution’s forensic evidence. We retain independent experts who can evaluate laboratory procedures, identify errors in testing methodology, and provide testimony that exposes weaknesses in the state’s case.
If you are dealing with charges for assault, sexual offenses, burglary, our attorneys will scrutinize every aspect of the DNA analysis, from collection to testing to interpretation, to ensure your rights are protected.
DNA evidence can be compromised in numerous ways. Contamination during collection occurs when an officer fails to change gloves between handling different items, when evidence is stored improperly, or when samples are processed in a laboratory that does not follow strict contamination protocols. Even trace amounts of foreign DNA can produce misleading results.
Secondary transfer is one of the most significant challenges to DNA evidence. This phenomenon occurs when DNA is transferred from one person to an object or location without direct contact, for example, shaking someone’s hand and then touching a doorknob can transfer that person’s DNA to the doorknob. This means your DNA can appear at a crime scene even if you were never there.
Additionally, mixed DNA samples containing genetic material from multiple individuals can be extremely difficult to interpret accurately. The statistical methods used to calculate the significance of DNA matches, including random match probability and likelihood ratios, are complex and can be challenged. Our attorneys understand these statistical methods and work with experts to identify weaknesses in the prosecution’s interpretation.
The reliability of DNA evidence depends entirely on the integrity of the collection and handling process. Evidence must be collected using sterile techniques, properly packaged to prevent contamination and stored under appropriate conditions. Every transfer of evidence must be documented in a chain of custody log.
Our attorneys obtain and review the complete chain of custody documentation for every piece of DNA evidence. We look for gaps in documentation, improper storage conditions, delays in processing, and any other irregularities that could compromise the integrity of the evidence. When we identify problems, we file motions to suppress the evidence or present expert testimony challenging its reliability.
Forensic DNA laboratories must follow strict quality assurance standards established by the FBI’s Quality Assurance Standards for Forensic DNA Testing Laboratories. These standards cover everything from analyst qualifications and training to equipment calibration, testing protocols and proficiency testing.
Our attorneys file discovery requests for the laboratory’s quality control records, proficiency test results, corrective action reports, and the qualifications of the analysts who performed the testing. We have found cases where analysts failed proficiency tests, where equipment was not properly calibrated, and where laboratories deviated from their own standard operating procedures. These findings can be devastating to the prosecution’s case.
We also examine whether the laboratory used the most appropriate testing method for the evidence in question. Different types of DNA evidence, such as touch DNA, degraded samples and mixed profiles, require different analytical approaches. Using an inappropriate method can produce unreliable results.
Modern DNA analysis increasingly relies on probabilistic genotyping software, computer programs that use complex algorithms to interpret DNA mixtures and calculate the likelihood that a specific individual contributed to a sample. While these programs can be powerful tools, they are also ‘black boxes’ whose inner workings are often proprietary and not fully transparent.
Our attorneys challenge probabilistic genotyping results by questioning the assumptions built into the software, the parameters chosen by the analyst, and the validation studies that support the software’s reliability. We work with independent forensic experts who understand these systems and can identify when the software’s conclusions are not supported by the underlying data.
A Blue Earth County man woke up one morning to find police at his door with a warrant for his arrest. He was charged with second-degree burglary after DNA found on a broken window at a local business was matched to his profile in a state database. He had never been to the business and had no idea how his DNA ended up there. What he did not know is that touch DNA can be transferred through secondary contact. He had shaken hands with a coworker earlier that week who had been at the business. That simple handshake may have transferred enough skin cells to create a partial DNA profile.
People in this situation often panic and try to explain themselves to the police. They assume that if they are innocent, the truth will come out on its own. This is a dangerous assumption. Without an attorney, they do not know to ask critical questions: How was the sample collected? Was the chain of custody maintained? What was the quantity and quality of the DNA recovered? Was the sample a mixture of multiple contributors? These technical details are often the difference between a conviction and a dismissal.
An experienced forensic DNA defense attorney will immediately retain an independent DNA expert to review the prosecution’s lab work. They will examine the collection procedures, the analysis methodology and the statistical calculations used to generate the match probability. In many cases, the defense expert will identify errors or alternative explanations that the prosecution’s lab overlooked. In this scenario, the attorney would investigate the secondary transfer theory, identify the coworker connection and present evidence that the DNA match does not prove the defendant was ever at the scene.
A conviction based on DNA evidence carries the same collateral consequences as any other criminal conviction, but the perceived scientific certainty of DNA can make these consequences even harder to overcome. Employers, landlords and licensing boards may view a DNA-linked conviction as particularly damning because they assume the science is infallible. The reality is that DNA evidence is only as reliable as the humans who collect, process and interpret it.
If you are convicted of a felony offense based on DNA evidence, your DNA profile will be permanently stored in state and federal databases under Minn. Stat. § 299C.155. This means your genetic information is available for comparison in future investigations, even if you are never charged with another crime. For individuals who are acquitted or have charges dismissed, Minnesota law provides a process to request expungement of your DNA profile from the database, but many people are unaware of this right.
Beyond the criminal record itself, a conviction involving DNA evidence can affect professional licensing, immigration status and family court proceedings. In custody disputes, the opposing party may use the conviction and the perceived strength of the DNA evidence to argue that you pose a risk to children. Our attorneys understand these downstream consequences and fight to prevent a flawed DNA analysis from destroying your life.
“DNA evidence is 100% accurate and cannot be wrong.” This is perhaps the most dangerous misconception. While DNA analysis is a powerful forensic tool, it is not infallible. Errors can occur at every stage: collection, preservation, extraction, amplification and interpretation. Contamination in the lab, degraded samples and analyst bias can all lead to incorrect results. The National Academy of Sciences has identified significant concerns about the reliability of forensic DNA analysis, particularly with low-quantity samples and complex mixtures.
“If my DNA was found at the scene, it proves I committed the crime.” The presence of DNA at a location proves only that your biological material was there at some point. It does not prove when it was deposited, how it got there or what you were doing at the time. Secondary and tertiary transfer can move DNA from one person to another and from one location to another without any direct contact with the crime scene.
“The DNA match probability of one in a billion means there is no doubt.” Match probability statistics are based on population frequency estimates and mathematical models that involve assumptions. Different laboratories using different methods can produce dramatically different probability estimates from the same sample. Additionally, these statistics do not account for the possibility of laboratory error, sample contamination or the presence of close relatives in the population.
“If the police have DNA evidence, there is no point in fighting the charges.” Many cases built on DNA evidence have been successfully challenged and dismissed. Defense attorneys regularly identify problems with collection procedures, chain of custody gaps, laboratory errors and flawed statistical analyses. An experienced forensic DNA defense attorney knows exactly where to look for weaknesses in the prosecution’s case.
Under the Fourth Amendment, law enforcement generally needs a warrant or your consent to collect a DNA sample from you. However, Minnesota law (Minn. Stat. § 299C.105) requires DNA collection from individuals convicted of or charged with certain felony offenses. If you are asked to provide a voluntary DNA sample during an investigation, you have the right to refuse. Our attorneys advise clients to never provide a voluntary DNA sample without first consulting with a lawyer.
You have the right to access all DNA evidence and laboratory reports in your case under Brady v. Maryland and Minnesota discovery rules. This includes the raw data, the analyst’s notes, the laboratory’s standard operating procedures and any quality control records. Our attorneys routinely request this information and have it reviewed by independent experts.
Under Minn. Stat. § 590.01, you have the right to petition for post-conviction DNA testing if you believe testing could establish your innocence. This right applies even after a conviction and can be a powerful tool for individuals who were convicted before modern DNA analysis techniques were available.
You also have the right to challenge the qualifications of the prosecution’s DNA expert and to present your own expert testimony. Under Minn. R. Evid. 702, expert testimony must be based on reliable scientific principles and methods. Our attorneys are experienced in challenging the admissibility of DNA evidence through Frye-Mack hearings in Minnesota courts.
The most effective defense strategy in DNA cases is a thorough, independent review of the laboratory work. Our attorneys retain qualified forensic scientists who examine every step of the analysis process. They look for contamination events, deviations from standard protocols and errors in the statistical calculations. In one notable case, an independent review revealed that the laboratory had failed to run proper negative controls, calling the entire analysis into question.
Challenging the collection and chain of custody is another critical strategy. DNA evidence must be properly collected, packaged, labeled and stored to maintain its integrity. Any break in the chain of custody creates an opportunity for contamination or misidentification. Our attorneys careful ly trace the path of every DNA sample from the crime scene to the courtroom.
In cases involving DNA mixtures, the interpretation of the data is often subjective and can vary significantly between analysts. Our experts use probabilistic genotyping software to independently analyze mixture data and frequently reach different conclusions than the prosecution’s laboratory. This can be powerful evidence that the DNA results are not as clear-cut as the prosecution claims.
Finally, we present alternative explanations for the presence of DNA at the scene. Secondary transfer, legitimate access to the location and innocent explanations for biological material are all viable defense theories that can create reasonable doubt. The key is combining technical challenges to the DNA evidence with a compelling narrative that explains the evidence in a way consistent with innocence.
Yes. While DNA testing is highly accurate when performed correctly, errors can and do occur. Contamination, secondary transfer, laboratory mistakes, and misinterpretation of results can all lead to incorrect conclusions. Our attorneys work with forensic experts to identify these errors and challenge unreliable DNA evidence.
Touch DNA refers to DNA that is transferred to an object through skin contact, such as touching a doorknob, steering wheel or weapon. Touch DNA samples are often very small and can be difficult to interpret accurately. They are also highly susceptible to secondary transfer, meaning the DNA on an object may not belong to the person who last touched it.
Yes. As a defendant, you have the right to request independent testing of DNA evidence by a qualified laboratory. Our attorneys can arrange for independent testing and retain expert witnesses to review and challenge the prosecution’s DNA analysis.
DNA can persist on surfaces for days, weeks or even years depending on environmental conditions. Factors like temperature, humidity, sunlight and cleaning can degrade DNA over time, but under favorable conditions, usable DNA profiles have been recovered from items that are decades old. This means the presence of DNA does not establish when it was deposited.
CODIS (Combined DNA Index System) is the FBI’s national DNA database that contains profiles from convicted offenders, arrestees and forensic evidence from crime scenes. When a DNA profile is developed from crime scene evidence, it is searched against CODIS for potential matches. A CODIS hit is not proof of guilt. It is an investigative lead that must be confirmed through additional evidence.
While rare, the planting of DNA evidence is not impossible. As DNA analysis becomes more sensitive, smaller and smaller quantities of biological material can yield a profile. This means that DNA from a discarded coffee cup, a cigarette butt or even a handshake could theoretically be collected and placed at a crime scene. Our attorneys investigate all possibilities when the circumstances suggest the evidence may have been tampered with.
Nuclear DNA is the most common type used in forensic analysis and provides a unique genetic profile (except in identical twins). Mitochondrial DNA (mtDNA) is inherited from the mother and is shared by all maternal relatives. MtDNA analysis is less discriminating than nuclear DNA but can be useful when nuclear DNA is degraded or unavailable, such as in hair shaft analysis.
The cost of an independent DNA review varies depending on the complexity of the case, but typically ranges from $5,000 to $25,000 or more for complex mixture cases. While this is a significant expense, it is often the most important investment in a case where DNA evidence is the primary basis for the charges. Our attorneys can help you understand the costs and explore options for funding expert review.
Familial DNA searching is a technique where a partial match in CODIS is used to identify a suspect’s close relative, who is then investigated as a potential suspect. Minnesota does not currently have a formal policy on familial DNA searching, but the technique has been used in other states. If you believe you were identified through familial searching, our attorneys can challenge the legality and reliability of this investigative method.
Our specialized forensic DNA defense team can help. Contact Birkholz Law today for a consultation.
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