Forensic Biology & DNA

Evidence may not be visible to the naked eye

Forensic Biology & DNA

Frequently Asked Questions

Does Riley Welch LaPorte & Associates Forensic Laboratories offer Contractual DNA Technical Review Services?

Yes. Riley, Welch, LaPorte & Associates offers contractual DNA technical reviews (in compliance with the FBI’s Quality Assurance Standards (QAS) for Forensic DNA Testing Laboratories) in support of government crime laboratories that have outsourced DNA casework to private fee-for-service laboratories. Staff DNA scientists are available who have significant experience conducting a large number of technical reviews from many of the major private DNA laboratories in the United States.

Significant levels of funding available to the government forensic laboratories for testing large numbers of sexual assault and other types of criminal cases has placed a large burden on them. Many laboratories have outsourced the testing to private laboratories, but private laboratories do not have access to upload eligible DNA profiles to the national DNA database, CODIS. Government laboratories must take ownership of the DNA data prior to upload of profiles through completion of a technical review. These technical reviews are an additional burden on government crime laboratories. Riley Welch LaPorte & Associates Forensic Laboratories is ready to assist in this area.

What is Forensic Biology?

Forensic Biology consists of two distinct areas of expertise. The first is Body Fluid Identification, often referred to as serology. Body Fluid Identification involves the use of a series of tests, typically chemical indicating tests, microscopic techniques and immunochromatographic tests, to locate and characterize potential body fluids. The second are of Forensic Biology is DNA testing. Once a body fluid is located and characterized, DNA testing is used to determine the possible source of the stain.

Which body fluids are important in forensics?

Body fluid identification techniques can be used to locate and/or characterize blood, semen, seminal fluid, saliva, feces, urine, sweat and contact stains. DNA profiles can be obtained from most body fluids.

What is the difference between presumptive and confirmatory serological testing?

Certain body fluid characterization tests are considered presumptive in nature. In other words, a positive test may indicate the presence of a body fluid but there are substances other than the body fluid in question that can cause a positive result. For instance, a chemical test for the possible presence of blood will give a positive test result in the presence of blood, but substances such as catsup, rust and soil may also cause a positive reaction. It is critical that an independent review of the results is completed so that the results are properly evaluated. A confirmatory test is a test that is specific for a particular body fluid and does not typically have false positive reactions. The number of confirmatory tests used in body fluid identification are limited.

How large of a stain is required for DNA testing?

DNA testing has become increasingly sensitive in recent years. So much so, that a stain does not need to be visible to the naked eye to be sufficient for DNA testing.

Can DNA testing be conducted on non-human body fluids such as wild game?

Primarily, forensic DNA has focused on human body fluids and forensic DNA. However, it is possible to conduct some testing on animal fluids.

How should biological evidence be packaged and maintained?

Biological evidence should be packaged and maintained much like food items are preserved. Typically, body fluids should be dried prior to packaging. They should be packaged in paper products such as envelopes or bags. They should never be packaged in a sealed plastic bag as this promotes bacterial growth and degradation. Sometimes it is beneficial to store the item either frozen or refrigerated.

Is contamination a concern?

Yes, forensic DNA testing is sensitive enough that the integrity of the item is often in question. It is critical that other items of evidence that may contain a body fluid are kept separated by time and space from each other. Additionally, it is critical that anyone that handles the evidence item take necessary precautions to prevent transfer of their own DNA onto the evidence. These precautions include the use of disposable gloves, masks and other personal protective equipment.

How many types of DNA testing technologies are available?

Forensic DNA testing encompasses a wide array of methods and technologies that are constantly being updated and improved. It is important to make sure an independent DNA scientist is consulted to ensure the most reliable and sensitive method is utilized based on the case circumstances and resources available. Forensic DNA testing may encompass autosomal STRs, Y STRs, Mini STRs, mitochondrial DNA, SNPs and DNA sequencing. Forensic DNA may be used in variety of civil and criminal cases, paternity cases and genealogy to name only a few.

What is a DNA reference standard and is one required?

DNA testing can be completed on a number of different body fluids and evidentiary items. However, in order to determine the possible source of the body fluid a DNA reference standard is needed. Often, a DNA reference sample is collected by utilizing a clean, sterile cotton swab and vigorously rubbing the inside of an individual’s cheek. At times, it may be beneficial to evaluate the evidence item by determining if a body fluid is present and develop a DNA profile prior to collection and submission of a DNA reference standard from possible contributors to the evidence item.

Who is authorized to conduct DNA testing?

Anyone can conduct DNA testing, but there are numerous guidelines and standards that cover laboratory accreditation, training and educational requirements. A laboratory should be accredited by a nationally recognized accrediting body such as Forensic Quality Services (FQS) and the American Society of Crime Laboratory Directors Laboratory Accreditation Board (ASCLD-LAB). Additionally, laboratory scientists conducting DNA testing should have a four year degree in a scientific area that includes coursework in genetics, molecular biology, statistics and biochemistry. There are many standards for DNA testing and it is best to have an expert evaluate if the standards are met and the testing can be relied upon.

What is a DNA Mixture?

Evidentiary items containing a body fluid may actually contain body fluids and DNA from more than one individual. For instance, following a sexual assault a nurse may collect a swab from the victim’s vaginal tract. A DNA analysis may detect DNA from the victim and a possible suspect or consensual partner. Evaluation of DNA mixtures can be very challenging for a scientist. Consideration of the relative amounts of DNA contributed by each person, potential for overlapping DNA types from the victim and additional contributor(s), artifacts and many other factors can impact the ability to state with certainty someone’s presence or absence within a DNA mixture.

How is the significance of a DNA match determined?

If a match between a DNA profile from an item of evidence and a reference DNA sample is determined, a statistical estimate of the relative frequency of the profile in the general population is typically provided. There are several different statistical methods used to develop the rareness of a DNA profile including Random Match Probability (RMP), Likelihood Ratio (LR), Combined Probability of Inclusion/Exclusion (CPI/CPE), Random Man Not Excluded (RMNE)and Paternity Index (PI). A qualified forensic DNA analyst would be able to explain the meaning of the statistical significance. Sometimes, if the frequency estimate of a DNA profile exceeds a laboratory-defined threshold they may not provide the numerical value and opt to state the person in question is the source of the DNA on the evidentiary item. This is termed Source Attribution. A qualified forensic DNA analyst can assist with explaining how the threshold is set and the meaning of the conclusion.

Do I need a scientific degree to interpret a Body Fluid Identification or DNA laboratory report?

Typically a body fluid identification report will state if a particular body fluid was observed on an evidentiary item. However, the reader must be cautious with the presumptive and confirmatory statements. DNA laboratory reports will typically provide for a match, inclusion, exclusion or inconclusive statement for each evidentiary item tested followed by a statistical estimate for the profile rarity. The forensic community is trying to simplify laboratory reports, but accreditation and legal standards require certain information be included. An independent qualified DNA expert can be instrumental in assisting others in interpreting and understanding the conclusions drawn and significance of any matches stated in a laboratory report.

I’m not a scientist, but rely on DNA testing as an investigator or legal professional. Can I be taught the basics of DNA testing and interpretation?

The simple answer, yes. DNA analysis is a multi-step process with many options for techniques, methods, equipment and software tools for interpretation and reaching conclusions. With that said, many qualified DNA analysts are experts at explaining the process and meaning of reports to non-scientists. There are many resources available to become familiar with forensic DNA testing.

Can DNA testing, even if DNA testing was previously conducted, aid cold case investigations?

Yes. DNA has improved tremendously over the past 5-10 years. The number of DNA markers evaluated, sensitivity of the chemistry to detect minor amounts of DNA, ability to interpret DNA mixtures and instrumentation available has opened even more evidence and crime types available to DNA testing.

DNA testing has been described as the “gold standard.” Is an independent review of DNA testing necessary?

The National Academy of Sciences issued a report in 2009 that described forensic DNA testing as having a strong foundation rooted in research and development. With that said, there are many opportunities within forensic DNA testing for independent evaluation. Conclusions can be overstated, mistakes in evidence handling can occur in the laboratory and statistical analyses can be inflated to name a few. An independent reviewer can provide answers to some of your questions and put the results in context with the questions being asked.


Jeffrey Nye is a Forensic Biologist with nearly 20 years of experience in the areas of Body Fluid Identification and Forensic DNA. He also has experience in the area of DNA relationship testing and interpretation. He is currently employed full-time as the Biology Program Coordinator and DNA Technical Leader, overseeing biology technical operations for a large state laboratory system.

Jeffrey Nye has extensive knowledge in the biological sciences, earning a Bachelor of Science degree in Biochemistry and a Master of Science studying microbial population structure and diversity in soil environments. His forensic experience includes analysis of thousands of biological cases using both serological and forensic DNA procedures, attendance at numerous national professional conferences and publishing in professional peer-reviewed journals.

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