The Mudville Gazette has a couple of posts that fill in a lot of gaps with the current story. (And, incidentally, suggest that the Ramparts scenario i discussed below may be coming to pass.)
First, this post discusses Seymour Hersh's veracity and his sources:
Seymour Hersh has had an amazing story dropped into his lap. A group of American GIs, caught on camera, abusing and humiliating Iraqi prisoners. Heinous acts. The wheels of justice were certainly turning, but nailing the abusive guards is not enough for the intrepid reporter. Indeed, since evidence indicates that one of those guard's attorneys most likely provided that information to Hersh, it follows that getting the higher ups was likely part of the deal.
This timeline of the abuse, investigation, and media stories is absolutely invaluable. Example:
Jan 14: SSG Frederick began writing his journal on Jan. 14, only a few hours after Army authorities fetched him for questioning and searched his quarters at 2:30 a.m. that day. He mailed copies to his mother, father, uncle and sister, and decided not to send it by e-mail for fear that the Army would see it first.
In January Army SSG Frederick began letters and e-mails to family members, and repeatedly noted that the military-intelligence teams, which included C.I.A. officers and linguists and interrogation specialists from private defense contractors, were the dominant force inside Abu Ghraib.
Blaming his superiors appears to be Frederick's defense and his lawyer is using a sometimes gullible and often ideological reporter to build his case.