Cases of identical twins being tried for the same crime may never happen again after a scientific breakthrough has found that there are subtle differences in their DNA

Forensic scientists have discovered that there is a subtle genetic difference in the DNA of twins which were previously thought to be entirely identical. The breakthrough means that there is now a definitive test to find out which twin has been at the crime scene or has fathered a child. In August 2013, detectives arrested Aftab and Mohammed Asghar, both 22, after recovering DNA from the jumper of 17–year–old girl who was attacked by at least three men in a Reading park at night. However the prosecution eventually offered no evidence against Aftab when analysis of his mobile phone showed that he was in another location at the time of the assault. Until now geneticists have not been able to prove that identical twins - also known as monozygotic twins - are not genetically identical. But in a breakthrough a forensic laboratory found the subtle difference at a genetic level which could prove vital in solving crimes and paternity cases involving identical twins. Scientists used high tech sequencing of DNA from sperm samples from one set of twins and from a blood sample from a child of one of them. Bioinformatics analysis in a forensics lab revealed five mutations, called "Single Nucleotide Polymorphisms" (SNPs) present in the twin father and the child, but not in the twin uncle. The results suggest that rare mutations will occur early after or before the human blastocyst (a pre-embryonic form) has split in two - the origin of twins.