I read with great astonishment your article regarding the court of appeal’s decision on proving paternity in the case of a child whose father could be either one of a pair of monozygotic twins (Court of appeal says it cannot rule on which identical twin fathered a child, 30 April). I was particularly surprised by the court’s statement that it was “not possible” to say which twin fathered the child. This is definitely not true. The germ cells of monozygotic twins differ with sufficient probability and to a sufficient degree to allow their respective children to be clearly assigned to either of them using molecular genetic techniques.

I and my colleagues first presented the idea for this approach back in 2012, and clearly demonstrated its practical feasibility in 2018. Of course, the required molecular genetic testing entails considerable costs (currently in the five-figure range). However, whether such costs would be so “very significant” (the court’s words) as to preclude genetic testing seems highly questionable, given the potential consequences of inaction for those involved.
Prof Michael Krawczak
Kiel University, Germany