Undermining a Partial DNA Profile

When navigating the legal system to prevent your name from being added to the Central Child Abuse Index, there's a pressing need to educate yourself.

The seriousness of this situation dictates your steadfast dedication to building evidence in your favor. You also must find every conceivable way to poke holes into allegations and how they've come about. With more facts on your side, and the less credible your accuser's story seems, the higher chance you'll be able to move on with your life from these horrific circumstances.

Unfortunately, there might be evidence being used against you that leverages science to hurt your cause. Since the methods are tricky to understand, many people mistakenly don't question its validity.

Or, if they do, they're unsure of what questions to ask.

If your case involved DNA evidence, you need to know about partial DNA profiles.

In breaking down the importance DNA profiling can have when mounting your defense, let’s look at a scholarly article called "Interpreting low template DNA profiles." (D.J. Balding, J. Buckleton, Forensic Science International: Genetics 4 (2009) 1-10.)

The study looks at how DNA profiles – gathered from low template samples – are interpreted. A problem arising in this scenario is when "drop-out" or "drop-in" revealed inconsistencies between samples collected at the “crime scene” and what's typically expected.

According to the research, this manner of a discrepancy is often overlooked by the legal system. It's an occurrence that proves unfair to defendants.

Before delving into this topic, you'll need to understand a few terms going forward:

DNA Profile

In the most basic of terms, a DNA profile is a full description of a person's DNA appearance.

Partial DNA Profile

Unsurprisingly, a partial DNA profile could potentially only describe one trait of a person, such as their hair color.

Low Template DNA

This is when only trace amounts of DNA are present in a sample based on the sample type. For instance, this can happen when someone handles an item.

Allele

Alleles can be the gene that's responsible for your hair color. It's a pair or series of genes on a chromosome that play a part in your hereditary characteristics, or in layman's terms, your appearance.

Allelic Drop-out

This is what happens when there's a failure to report in a DNA profile obtained from that sample.

Allelic Drop-in

Here's what happens when trace amounts of DNA produce questionable allele(s) in the profile from a crime scene or plasticware in a lab.

Locus

On a chromosome, a locus is a fixed position where a unique gene is located.

Without the presence of degradation or inhibition of a sample, both drop-out and drop-in generally don't occur in reliable samples. Conversely, the chances of these two occurrences are drastically increased during the reduction of a DNA template when subject to additional environmental exposure.

Even full DNA profiles can match with someone who isn't the culprit. Partial profiles can match up with even more people than a full profile, resulting in an increased likelihood of a false positive identification.

In 2003, Richard Bates was convicted in London for the murder of Marilyn Garside. It was believed that Bates was paid by Garside's husband to commit the act.

When looking at the DNA evidence used against Bates, three of Bates' loci weren't reported from the several crime scene samples, and profiling runs under varying lab conditions. In these samples, there's strong evidence that drop-out could have occurred.

When drop-out is plausible, ruling out drop-in becomes a significant challenge.

It's also worth noting that alleles not attributable to Bates were evident in some crime scene profiles. Unsurprisingly, this wasn't the case with the most incriminating profiles.

After a series of appeals and retrials, Bates was unsuccessful in fighting for his freedom after attacking the credibility of the DNA.

In short, it was ruled in court that these partial or low template profiles are admissible as evidence, but it must be established that it only paints a partial picture and is explained as incomplete.

If the evidence being presented against you stems from a partial DNA profile, you need to know that the evidence against you is not ironclad.

By mounting your best defense, low template or partial DNA samples may be overcome.