MR. HADDAD’S story tells two truths of modern Iraq: the exile of educated technocrats from government service in favor of the patronage appointments of party-aligned officials who bend to the will of a powerful prime minister, and the vast wealth that is available to the well-connected in a society where the majority of citizens live in abject poverty.

With violence in Iraq increasing, the government has responded with some of its harshest crackdowns yet on Sunni areas, casting a wide net in pursuit of terrorism suspects, arresting the innocent and guilty alike. Which is good news, of course, for Mr. Haddad, whose business is booming. He said his phone was constantly ringing, with calls coming in from Anbar, Mosul and Tikrit, Sunni areas where young men are filling the jails.

Through Mr. Haddad’s efforts, Abu Hussein, a Sunni police officer in Samarra, was recently released from jail after being held for a year on terrorism charges that he said were false and made by an anonymous informer. That is standard practice here. Many Iraqis, some of whom used to feed tips to the American military in exchange for money, now earn a living informing on their neighbors. The problem, say human rights activists and Iraqi officials, is that the information is often false.

After his arrest, a friend told Abu Hussein about Mr. Haddad.

“They said he is the one who defends the innocent people,” he recalled. “The Iraqi law is protecting those informers, but never the innocent people.”

He continued: “He is a Shiite man, but he defends the Sunnis. He knows what is right and wrong, and sect is not important.”

Mr. Haddad said he takes only cases in which he is convinced the defendant is innocent. As a result, the mere fact that he has chosen to represent a particular client, not to mention his fame and reputation gained from the Hussein trial, is sometimes enough to ensure an exoneration.

Like many educated Shiites and Kurds oppressed under the former regime, Mr. Haddad left the country in the 1990s after spending time in jail and seeing two of his brothers killed by the government. He became a lawyer in Oman, where, he said, he was “a big man. I had a driver, a big house.”