As the Anthony Weiner Twitter whodunit trundles on into almost a full week, it remains unclear where the now-infamous photo came from. To help shed some light on this, I contacted Hany Farid, a renowned expert in forensic photographic image analysis. (Farid was consulted by the Associated Press in debunking the fake Bin Laden death photos, and has also teamed up with Microsoft to develop anti-child-pornography software.) Using compression data and metadata from millions of photos, Farid and his colleagues at Dartmouth have developed a database that matches photos to the digital cameras that took them.

Anthony De Rosa of Reuters has already shown that the Weinergate photo’s metadata don’t match the metadata of another photo known to have come from the congressman’s Blackberry. I sent both photos to Farid, who analyzed them. Farid confirmed that the photo known to have come from Weiner’s camera was “inconsistent” with the controversial photo. In fact, Farid says, the photo appears not to have come from a Blackberry at all. But here’s the even stranger part: The controversial photo does not match any camera in Farid’s database, which consists of about 15,000 kinds of cameras, phones, and tablets.

What does this mean? One possibility is that the photo comes from a model so recent, it isn’t yet in Farid’s database. Judging from the photos on the congressman’s yfrog account, he does not own such a model. (The model of camera from which Weiner’s yfrog photos were taken would have led to a match in Farid’s database.) Another possibility is that something about the photo was tampered with, causing it not to match up with any model in the database.

Neither possibility, it should be noted, precludes Weiner from being the man in the photo. But, in either case, it seems unlikely that the photo went directly from Weiner’s Blackberry to Twitter.