Wozza,
Here is a thread from about eight years ago that may contain the info you are asking for.
http://www.jehovahs-witness.net/jw/friends/24050/1/TWO-WITNESSES-to-secret-sin
Also, the Bible does not say that the two witnesses are "eye -witnesses" as the WT claims. That is wt-speak.
The Bible says at the "mouth of two witnesses" . As the post link above says, the elders/judges of Israel were to make a serious enquiry about the matter.
So a doctor or an investigator, who is not an eye-witness to the event should be able to give testimony with his mouth such as dna evidence or other forensic evidence.
belbab