Examining DNA

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.