A London court is unable to determine which of the two brothers is the baby’s father, as conventional DNA methods cannot distinguish between the two. It will be necessary to sequence each twin’s entire genome, which is not only a time-consuming but expensive process
An unprecedented case in the London courts brought science and law face to face: a woman who had sex with two identical twin brothers “in four days” saw the birth of a baby whose biological father cannot be identified with conventional DNA methods.
the mother, whose name was not revealed, registered the child, known as P., as being the daughter of one of the brothers. But the other brother appealed to the court, contesting the decision and asking for the two to be legally recognized as parents.
In the first instance, the judge refused to remove the alleged father’s name from the certificate, and the case was referred to the Court of Appeal in London, where a panel of judges concluded that it was “not possible to determine” which of the twins is P’s father.
However, according to the responsible judges, although traditional DNA tests cannot distinguish twins, science may be able to in the future. Until then, the brother registered as the father will have his parental responsibility suspended until further deliberation by the Court.
“Currently, the truth about P.’s paternity is that his father is one of these two identical twins, but it is not possible to determine which one. It is possible, and even likely, that when P. reaches maturity, science will be able to identify one of the parents and exclude the other twin; however, for now, this cannot be done without very high costs, and therefore his ‘truth’ is binary and does not come down to a single man,” the judges wrote in the judgment.
The case, described as “curious and rare”, was analyzed by biochemist David Marçal who, in an interview with Diário da Manhã on TVI (from the same group as CNN Portugal), explained the scientific difficulty.
“Identical twins result from the same sperm and the same egg that fuse and then this fertilized cell, which is the zygote, divides, but it doesn’t divide in the normal way, staying together. It divides in a simple way, giving rise to two zygotes. Therefore, theoretically, identical twins should be indistinguishable in DNA. That’s not exactly true, because in that division, that division is not perfect, therefore there are some errors and there are therefore some differences”, stated the biochemist.
According to Marçal, it will be necessary to sequence the complete genome of each twin and the baby several times, in addition to using advanced bioinformatics analyses, to find rare mutations present only in the sperm of one of the twins.
“It is necessary to sequence the entire DNA of each of the twins and the baby, and it is not enough once. It takes time and money, because it is not enough to sequence each of the genomes once, because sequencing can give rise to errors, so we have to be sure that the differences found are not a technical error, so we have to sequence each of the genomes about 30 times”, he explained, adding that even then “there is no 100% probability of being able to discern paternity”.
The court has not yet decided the final outcome of the case, so the trial continues.
