An example of an offline breadcrumb: signatures. We photographed thousands of documents in Syria. Take Mohammed Kanjou al-Hassan, for instance, a military prosecutor. We could match his signature, and see he ordered to keep info from families of detainees who were killed.

Despite facing sanctions, some of these individuals were rarely, if ever, seen or photographed in public, making it much easier for them to move under the radar. An example: Bassam Hassan, one of Assad's most senior henchmen, has long been misidentified. nytimes.com/video/world/...

As we embarked on this investigation, we immediately faced a challenge: whom to focus on when so many played a role. We began with those that were sanctioned by the United States and the European Union.