How Reliable is DNA Evidence


These days, criminal investigations are never without DNA testing. It doesn’t really come as a big surprise since it is something that has helped to identify criminals since the day that it came into being. From real-life crimes to those that are depicted most, especially in TV shows about forensic investigators, it would seem like DNA testing is the gold standard for collecting evidence and ultimately putting the guilty behind bars.

To put it simply, DNA testing is 99.9% accurate. It has come a long, long way since its birth in the mid-1980s — it has evolved into its current form as we know it, which is absolutely reliable. As a matter of fact, even the kind that is carried out in the comfort of your home for learning about your lineage is regarded as very accurate.

However, some people can’t help but wonder if DNA really makes it so much more effective for crimes to be solved. They tend to question the accuracy of DNA testing as well as its susceptibility to being tampered with. Can they or their loved ones be convicted of a crime they never committed because of false results?

It is true that DNA testing can offer peace of mind as it can help to identify criminals so much easier now more than ever. Sadly, it can also cause fear to an innocent person who is being linked to crime due to some DNA-related matters.

If you are one of these people who are having doubts as to the use of DNA for pinning down criminals, keep on reading — below are some of the things you need to know about the reliability of DNA evidence.

First Things First: The Accuracy of DNA Testing Revealed

But before we nosedive into the reliability of DNA evidence, there is one important thing that we should do. Let us first answer a question with a crucial foundational role in the use of DNA for evidence: how accurate is DNA testing?

Various DNA testing methods are in existence. However, none of them is as simple (although on the unpleasant side) as filling a small plastic tube with your saliva.

If you have already paid for and submitted a DNA testing kit for uncovering your ancestry, then you know exactly just how gross it is. Well, this DNA testing approach is known to be highly accurate. So just imagine the sheer accuracy of other methods out there, such as one that involves analyzing the blood.

Yes, for the record, DNA testing is highly reliable. This does not mean, however, that it is something that is foolproof. Although it is true that the science of DNA analysis is almost 100% accurate, a problem still exists. The results can actually be affected by DNA contamination or tampering with.

For example, that saliva you are going to submit to the ancestry or genealogy site of your choice could, in fact, be contaminated. Such is a matter that is likely to come into being while you are spitting into the plastic tube that came with the DNA testing kit.

More often than not, contamination of your DNA sample is the result of eating, drinking, chewing gum, brushing your teeth, or smoking at least half an hour before the collection of your saliva.

Contamination of your DNA sample in the form of a tube filled with your saliva may also take place inside the laboratory. This could happen if the employee who is tasked at testing your saliva is not that experienced or careful. Using a tool that is contaminated with the DNA of someone else, for instance, can have an effect on the results.

The results churned out by a machine will also have to be interpreted by a person afterward. We all know for a fact that when providing an opinion is concerned, there is always room for a false impression. The report that ancestry or a genealogy site provides you with is produced by a machine that was later on interpreted by a human being.

It is not DNA testing that is questionable. But rather, it is the collection of DNA samples to be tested that can cause doubts in some. The experience or cautiousness of the technician is also a contributing factor.

Today’s TV Shows are Giving the Wrong Impression

Are you a huge fan of TV series in which the leads are forensic investigators trying to solve crimes? No one can blame you for being hooked on them.

It is plain to see that one episode after the other can get your heart pumping — nothing can be more exciting than watching law enforcement trying to crack the codes in order to track down perpetrators and put them behind bars, thus bringing justice to the hapless victims!

Because you lovingly devour these types of TV shows, then you may have the impression that DNA evidence is everything. When it comes to solving the toughest crimes, you believe, it is DNA testing that can save the day.

Unfortunately, real-life forensic experts confirm that these TV series that are filled with action and suspense are causing the viewers to get the wrong impression.

They add that the effectiveness of DNA evidence when it comes to solving crimes that are yet to be solved is being exaggerated by these TV shows. No, they are not saying that DNA testing is not dependable. Just like what we have discussed earlier, today’s DNA testing is 99.9% accurate.

What actual forensic experts (and not the ones on TV) are saying is this: DNA tests won’t really give law enforcement all the details they will need in order to get their hands on those elusive criminals.

It is not just the die-hard fans of these TV shows putting the spotlight on forensic investigators who are getting the wrong impression. According to experts, so many of the jurors in criminal trials strongly believe that DNA found at the crime scene is enough to convict a person of a crime.

What’s more, they add that a lot of judges are sharing the very same opinion! Such can definitely be blamed on TV series wherein every crime to solve is solved with the help of DNA evidence.

One must not forget what we have discussed earlier — you know, that contamination is a possibility. Then there is also the fact that a desperate criminal or a vengeful investigator may tamper with DNA at a crime scene! Indeed, there are many things that could impact the reliability of DNA evidence.

Yes, it cannot be denied that DNA evidence can help a lot when it comes to tracking down criminals. Through such, it can become easier for law enforcement to figure out which one among a long list of suspects could be the person that they are looking for exactly.

It is important to know, however, that the DNA evidence should not be taken as the ultimate proof. Instead, it should be regarded as just one of the various pieces of evidence.

Definitely, it is a good idea for everyone to watch less of these TV series and spend more of their time reading about DNA testing coming from reliable sources on the web.

Through this, a lot of the myths concerning DNA being used as evidence and ultimately for solving crimes can be dispelled. And speaking of myths, later on in this article, we will tackle some of those that so many people believe as facts.

DNA Can be That of Criminals and Many Others, Too

Since it came into being back in the 80s, DNA testing has made it so much easier for law enforcement to pin down criminals. DNA testing has also helped to release people who were wrongfully convicted in the past prior to the invention of such science.

At a crime scene, there’s usually a pair of DNA that can be obtained. They are the DNA of the victim and the DNA of the perpetrator. It’s because of the DNA of the criminal left at the scene why forensic investigators are able to enjoy a much-needed head start, thus increasing the likelihood of the victim and his or her family attaining justice as soon as possible.

As a matter of fact, so many of today’s crimes have been solved in no time with the help of DNA evidence.

Sadly, DNA testing may sometimes point the experts to the wrong person. So, in other words, it could, in fact, cause a completely innocent individual to be suspected or even convicted of a crime.

No, this has nothing to do with the accuracy of DNA testing. The precision of DNA testing cannot be stressed enough — it will surely reveal the identity of the individual to whom it belongs.

The problem lies in the fact that in some cases, DNA specimens present at a crime scene are not only those of the hapless victim and the ruthless criminal. There is a possibility for some of them to have come from other people — those who were nowhere near the crime scene at the time the nightmare happened or have nothing to do with the crime.

So how could a totally innocent person’s DNA wind up at the crime scene? Did it magically hop from his or her, say, saliva to the place where the crime took place?

This surprising phenomenon can be blamed on what scientists refer to as “secondary transfer DNA”. There are some reporters or journalists who prefer to call it “touch DNA.” No matter the case, it’s quite evident what it is: DNA that made its way to the crime scene for some reason.

No mystery surrounds secondary transfer DNA because there is usually a perfectly sensible explanation for it. As a matter of fact, it is something that can take place by means of a number of ways.

For instance, the DNA of the person who sold and handed the ax to the murderer could be present at the crime scene. The DNA of a person who shook the hand of the criminal before he or she committed the crime could also be found at the crime scene.

Then there is also the possibility of the DNA of an innocent person being strategically planted at the crime scene of a cunning criminal!

So in other words, in some instances, DNA found at the crime scene can belong to many different individuals, some of them have nothing to do with the crime. It’s for this reason why just because DNA testing can point the police to someone doesn’t mean right away that he or she should be convicted and locked up without delay. 

Myths Concerning DNA Testing for Solving Crimes

Just like what was said earlier, different myths are surrounding DNA testing. This is usually brought about by hearsays as well as TV shows on forensic investigators catching criminals by means of DNA left at the crime scene.

It is important for us to separate fact from fiction. This is true, especially if the goal is to have a better understanding of matters concerning DNA evidence, such as its limits when it comes to solving crimes that are hard to crack.

One of the biggest myths out there regarding DNA is that it can actually be used for precisely recreating the face of a criminal. Knowing how the perpetrator of a crime looks can certainly make the job of the police so much easier. Thanks to DNA testing, apparently, CCTV footage and witness accounts are no longer needed for solving crimes.

Evidently, this also eliminates the need for an artist to sketch the face of the suspect based on the descriptions of witnesses. But because we all know that beauty is in the eye of the beholder, it’s not unlikely for these sketches to be inaccurate.

As a matter of fact, according to a report, those hand-drawn faces by experienced artists are only about 9% accurate when it comes to producing similarities to the faces of suspects. This is why coming up with the faces of suspects by means of their DNA samples can be quite promising and also exciting.

Because DNA is the one used, it would seem like it is for certain that a precise computer-generated mug shot of criminals can be produced.

If truth be told, the science for it exists these days. It’s called DNA phenotyping. Unfortunately, the creation of the exact face of a criminal’s face by means of DNA left at the crime scene is not possible.

Basically, DNA phenotyping is all about identifying genetic markers found in DNA, such as that which can be found in a drop of blood on the body of the victim that is someone else’s.

By means of these so-called genetic markers, forensic experts are able to have an idea of how the criminal would look if he or she were in front of them.

There is no denying that this technology called DNA phenotyping is a real thing. However, you should know that this science is, in fact, still in its early stages — in the US, the first of its kind was used only back in 2005 in Brooklyn.

Here is the deal with DNA phenotyping: it can only give forensic investigators the sex, hair color, skin color, and at times eye color of suspects. Sadly, it cannot provide the shape of the face, size of the lips, and other physical traits. Of course, in time, DNA phenotyping will evolve further, and criminals are going to have cold sweats when that day comes!

But until this breakthrough takes place, experts can only use DNA phenotyping for narrowing down their search. So in other words, DNA phenotyping, despite its current limited capabilities, is not useless entirely.

The Takeaway About the Reliability of DNA as Evidence

It cannot be denied that DNA testing is capable of producing results that are almost 100% accurate. This is the reason why DNA evidence can prove to be essential for solving crimes that would otherwise be extremely challenging to solve. Forensic investigators find DNA testing as vital for piecing together the clues, which is important for bringing justice to crime victims as well as their loved ones.

However, using it alone is not enough to convict a person of a crime. Just like what’s mentioned above, secondary transfer DNA is something that can link a completely innocent individual to the crime or crime scene. Furthermore, DNA testing cannot be used to produce the exact face of a criminal.

There are all kinds of myths surrounding DNA testing, and that is why the thought of using DNA as evidence can bring about doubts and even fears in some people. It is for certain that you will feel the same if one day forensic investigators showed up at your doorstep, wanting to ask you some questions about a person that was recently found dead.

It is a good thing that DNA evidence is not the only one used by law enforcement and during court proceedings in figuring out if a suspect is guilty.

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Ryan Sanders

Ryan Sanders is an aspiring genetics science enthusiast. His journey started with curiosity about his roots. He keeps learning more about genetics every day.

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