Thousand of crimes have been solved thanks to DNA testing. Better than a fingerprint, a DNA print is far more unique. In a murder case involving identical twins (such as the case with Ronald Smith and Donald Smith) DNA testing results can prove ambiguous: which twin did it? The article tells you more about DNA twin testing and twins.
A bit more Detail about Identical and Fraternal Twins
Identical twins, less frequently called monozygotic twins, are formed when a single sperm fertilises an ovum (a female egg) and the fertilised ovum splits at a later stage to form two separate embryos (usually splitting occurs somewhere between 4 -13 days after conception). The twins often share the same amniotic sac. Identical twins have their entire DNA in common and are thus, essentially, genetic replicates of each other. Identical twins are always of the same sex.
Fraternal twins, also called dizygotic twins, are formed when two sperm cells fertilise two ova. It is possible for women to ovulate two eggs rather than one as normally is the case; the reason for the release of two ova is not known. The resulting twins are just like siblings or half siblings and in some languages are in fact referred to as ‘false twins’.
Atlanta Identical Twins: DNA Testing does not Solve Murder Case
As stated, identical twins are genetic replicas of each other. DNA testing to solve murder or other cases of crimes is extremely reliable. The chances of two randomly selected individuals sharing the same DNA is 10 billion: 1. However, in the case of identical twins matters are more complicated because of the fact that their DNA is identical.
Atlanta, USA, 18th July 2008. Single mother of three, Genai Coleman, is waiting to collect her children. During a carjacking, Coleman’s car is suddenly shot at, killing her. Luckily, there were witnesses who gave a description of the attacker as well as surveillance cameras. DNA testing of evidence found at the scene quickly helped track down the perpetrator. Donald Smith was arrested for the murder of Coleman. Police thought the case was solved until Donald claimed his identical twin brother was the guilty one. This meant that DNA testing could no longer be used as evidence as the twin’s genetic profiles are identical and thus, any genetic evidence collected at the scene could belong to either of the twins.
Returning to the crime scene investigators decided to focus on fingerprints rather than DNA. The fingerprints found did in fact match Donald’s twin brother’s. Ronald Smith was charged with the murder and imprisoned. This is a very rare case were finger printing is a better alternative than DNA criminal profiling.
Identical Twins do not Share the same Fingerprints: Why?
In all respects, identical twins are the same and the same genes are activated. In fact, as a DNA test could show, their DNA is the same and they are physically indistinguishable one from the other. However, identical twins do not have carbon copy fingerprints; this is because human fingerprints are not solely the result of genes. They are somewhat more complex and their formation happens in the early stages of pregnancy. The environmental conditions surrounding the embryo and stresses in the uterus are crucial. The following are all factors that influence fingerprint formation and development:
- Length of the umbilical chords
- Blood pressure
- Finger growth rate towards the end of first trimester
People, even identical twins, may have similar fingerprint patterns but they will unlikely be the same for all ten fingers.
DNA twin testing and all related tests are highly reliable and accurate. The Murder case here discussed involving Ronald Smith and Donald Smith required fingerprints because identical twins are rather special in terms of genetic makeup; perhaps luckily for criminal investigations, there are not too many identical twins around.