Stringfellow Hawke said:
There should be a preponderance of evidence to try and convict anyone of a crime. Not a suspect DNA test. If evidence supports the DNA from the victims and the accused, prosecute. If it does not, then he should not be charged.
The standard to charge someone and move to trial is probable cause. The standard for conviction is beyond a reasonable doubt.
In this case, there were multiple women in one area who did not know each other and reported strikingly similar rape events. Their rape kits all matched to the same suspect. The police knew they were looking for one rapist. The available databases at the time (people who had submitted DNA to police) did not find a match. The case went cold.
They reopened the case, uploading the DNA profile into a public database and matched a distant relative to the suspect. Contrary to popular belief, they don't typically use Ancestry or 23andMe. They usually use a database called GEDMatch.
They used genealogical records, birth announcements, etc. to built out family tree, likely going back to the great great grandparents and worked their way down each branch until they found someone that lived in the area at the time of the rapes and was the right age and sex. This is the Boston area so you have a lot of big Catholic families to sort through. It took a lot of time.
Once they narrowed down to one or a few people, they gathered DNA on discarded items and were able to get a match.
Considering they found this guy's semen DNA (assuming they found semen) on all of these women who reported they were raped, in the area he was living, at his age and appearance that matched the witness' descriptions, it's hard to find any sort of doubt let alone doubt that is reasonable.
