I believe they said "scientific evidence" would be presented in court. They already provided photographic evidence and of course Candace and her band of lunatics claimed it was all doctored.
We'll have to see what evidence the Macron's produce, but all they really have to do is bring her brother into the courtroom with her.
Honestly, I don't think this is ever going to see a courtroom. How do you hold a trial involving the President of France and his wife without it becoming a circus, which I am pretty sure Candace's lawyers will try to do if this goes to court. But she has already filed a motion to dismiss the case, which I think will fail. A good judge will try to force a settlement based on evidence he will see or hear alone in his chambers. My guess is, if Macron provides evidence to the judge that she is a woman and not her brother, the judge will pressure Candace to settle by issuing a public apology and vowing never to mention this macron's again. I doubt the Macrons really want her money which I am sure she has protected by now.
I also don't think that it is necessary to do a DNA test in front of the judge or in the courtroom as a public spectacle. There are ways to get it done and satisfy the rules of evidence. Remember, this is a lawsuit not a criminal trial. Preponderance of evidence is the standard.