Csa and dna test

Long story short my parter took a dna test for a child he thought was his but came back that they wasnt (mother sleeps around) we have a legal one he can use in court can he use this to show csa that hes not her dad or does he have to do another because he wants to use or legal one because he doesnt want to upset the child more and put her through more unnecessary testing with more strangers