C brings a clinical negligence claim for serious brain injury said to have been caused due to hypoglycaemia following his birth. 
C’s case on causation is that the cognitive, behavioural and emotional deficits from which he suffers were caused by damage to the brain caused by hypoglycaemia in the period shortly after his birth. There is no dispute that he suffered hypoglycaemia, the issue is whether the hypoglycaemia led to any brain injury. D has not yet provided a defence but the letter of response states that “there is no clear evidence of a prolonged period of hypoglycaemia associated with neurological function and there is no evidence in the documents that the claimant suffered permanent brain injury as a result of hypoglycaemia. C is put to proof.” 
D has made an application for the court to order that C, and both his parents, provide a blood sample for the purpose of genetic testing and in default that the claim be stayed. D is of the view that there is possibly a genetic cause for C’s condition which is unrelated to the actions of the defendant. D contends that testing and expert evidence in the field of genetics is reasonably required in order for the Court to determine the issue of causation. 
in a case where it appears that D’s position that there may be a genetic cause has arisen more from the view that there is no other known cause than from a positive view that his symptoms fit with a particular genetic cause or indeed that there is an unknown but likely genetic cause, I am of the view the balance lies in not making the order. The effect of the testing on C and his parents is significant and in my judgment outweighs the potential benefit to D in having a 1 in 4 or 5 chance of positively proving a genetic cause.