Home > Forensics > Effectiveness of DNA Identifiers

Effectiveness of DNA Identifiers

By: Ian Murnaghan BSc (hons), MSc - Updated: 7 Mar 2014 | comments*Discuss
 
Dna Identifier Identification Ruling

Using DNA to identify a person is not as much of an exact science as some people may believe. For example, there is a great deal of judgment and common sense that must be involved and also a consideration of other types of evidence in criminal investigations. While in some instances, the match may be 'perfect' enough to conclusively show that evidence links to a suspect, other times it may not be so clear-cut and the match may be less obvious.

Using DNA to Create a Match

While humans share much of the same DNA, there are still some variations that can be exploited for identification purposes. By comparing the regions that differ from one person to another, scientists can match up evidence or link two people together from a familial line as well as perform other useful applications. There are thirteen DNA regions that are analysed to create a DNA profile for criminal investigations.

Making a DNA Match

You may be wondering just how accurate this type of identification is, given that a mistake could result in major consequences, particularly in instances of proving guilt or innocence in a crime.

DNA evidence needs to be used carefully and with common sense as well. If you think about evidence in a criminal investigation, you know that common sense will dictate that one piece of evidence in itself is not necessarily strong enough to point to a specific perpetrator. For instance, if investigators knew that a footprint was left from a size eight shoe, this would not be enough because many people have shoes of this size. If a piece of black hair were left behind as well, the two pieces of evidence would be more helpful in narrowing down to a perpetrator.

Try to consider DNA evidence in that same light. A forensic scientist will investigate a DNA sequence by looking for a match in specific bits of the DNA sequence. While one or even a couple of matches are not that strong to indicate a match between two DNA profiles, four or even better - five - are significantly stronger and can provide more confidence that there is an accurate match between two profiles.

Also keep in mind that there may be several suspects in a case. This means that it is not simply a case of looking for a match between evidence and one person, but it requires comparing the number of matching regions collectively from one suspect to another. One suspect may only show a few matching regions, another may show half and yet another may show all thirteen. The probability would therefore indicate that the suspect with all thirteen regions matching the evidence is the culprit.

Matching and Probabilities

Probability is a large part of making a DNA match in a crime scene investigation. Investigators must look at the probability of a person matching a random sample of DNA evidence. The probability is highest for a person matching a random sample at just one region and this would not be a strong enough match to show that the person was at the crime scene. The probability goes down with each subsequent region match until all thirteen regions match, which would indicate a probability of virtually zero.

DNA evidence can sway a case toward a suspect but it is clearly not always a simple, straightforward process of analysing a suspect's DNA and immediately ruling that person out or conclusively pointing the finger. Depending on how close the DNA matches, other pieces of evidence will need to be taken into account to help determine a person's innocence or guilt. Still, despite the challenges of using DNA to identify a person, we are fortunate to have this technology because its benefits far exceed any difficulties.

You might also like...
Share Your Story, Join the Discussion or Seek Advice..
Why not be the first to leave a comment for discussion, ask for advice or share your story...

If you'd like to ask a question one of our experts (workload permitting) or a helpful reader hopefully can help you... We also love comments and interesting stories

Title:
(never shown)
Firstname:
(never shown)
Surname:
(never shown)
Email:
(never shown)
Nickname:
(shown)
Comment:
Validate:
Enter word:
Topics
Latest Comments
  • annabanna
    Re: All About DNA and Proteins
    very good information and easy to understand
    26 March 2020
  • LivLee
    Re: The Properties of DNA
    Can somebody please tell me at least 5 or more characteristics/facts about DNA?
    4 March 2020
  • Patty
    Re: DNA Testing for Pets
    Can you test my dogs ashes just for breed so I know I got the right ashes back?
    2 March 2020
  • Julia
    Re: The Importance of DNA
    I've been looking for the roles and challenges of DNA in modern biology Pls I need help on it
    2 March 2020
  • Vennah
    Re: DNA Test after Death
    I lost my Baby last year may and the father is saying that the child is not his i have a 5year old child by him what can l doo too proof to…
    12 February 2020
  • Seahawk
    Re: DNA Test after Death
    My wife of 30 years was wrongfully convicted of trumped up charges from the prosecution no evidence at all, she had seizures and kept telling…
    2 February 2020
  • yoks
    Re: DNA Testing for Pets
    my best friend jakey passed away and i wish to adopt another dog through jakes lineage jake was microchipped twice and i still have his…
    20 January 2020
  • Building
    Re: DNA Test after Death
    Why is a building called a building if it’s already built?
    14 January 2020
  • Joe
    Re: DNA Test after Death
    One sunny day joe was in a great mood. Bob saw him from the other side of the room. But little did he know he was a horny bastard. Joe felt…
    13 January 2020
  • Slave Owner
    Re: An Overview of DNA Functions
    I hate Abraham Lincoln I was fine with my Slaves, they would do everything for me and now they are all released, we should kill…
    13 January 2020