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Iraq's first major trial dealing with the country's savage Sunni-Shiite sectarian killings is tainted by politics, critics say — an ominous sign for those hoping for justice for tens of thousands of victims of street executions, bombings and kidnappings.

The defendant, Vice President Tariq al-Hashemi, says charges that he ran Sunni death squads are part of a political vendetta by Prime Minister Nouri al-Maliki, a Shiite. Al-Hashemi's nine-member legal team walked out in protest in the second court session late last month, citing judicial bias. And the prosecution's case relies heavily on the testimony of co-defendants, that the defense claimed was coerced, pointing to one who died in custody.

More broadly, regardless of the merits of the case against al-Hashemi — the highest-ranking Sunni in Iraq's leadership — the Shiite-dominated government has shown no sign of trying to prosecute those behind Shiite militias behind slayings of Sunnis. Several of those militias were linked to Shiite political parties that are now crucial backers of al-Maliki's government.

Government spokesman Ali al-Dabbagh denied any bias in charging al-Hashemi or that he was singled out, saying the case was strictly a legal matter. "Courts look into the crime itself, not the sectarian background" of the suspect, he said.

However, al-Maliki himself has acknowledged that politics played a role in the timing of the charges against al-Hashemi. The prime minister has said he was aware of incriminating evidence against the vice president three years ago, but didn't press the case then "for the sake of the political process."

Prosecutors charged al-Maliki's often irksome rival only in December, a day after U.S. troops left Iraq, effectively ending the direct influence in Baghdad of the United States, which had pressured Sunnis and Shiites to get along. Al-Hashemi fled before he could be arrested, first to Kurdish-run northern Iraq where he was out of Baghdad's reach, then abroad.

Iraq remains paralyzed by the sectarian power struggles even if violence has dropped off since the worst bloodshed of 2006 and 2007.

Some say that even if there was a political will to go after the major perpetrators, regardless of sect, Iraq doesn't have the tools for such an enormous task, particularly an independent judiciary not intimidated by politicians or the threat of violence.

"There has not been any investigation into the atrocities," said Samer Muscati, a researcher at the international group Human Rights Watch. "The killings were on such a scale, and given the priorities of the current government and ongoing violence, it is hard for them to look at what happened a few years ago."

Long-running tensions between Iraq's Shiite majority and Sunni minority exploded three years after U.S.-led forces invaded Iraq in 2003 and toppled Saddam Hussein, a Sunni. In February 2006, al-Qaida-linked insurgents bombed a major Shiite shrine, an attack that unleashed tit-for-tat killings, forcing hundreds of thousands of Iraqis to flee their homes and pushing the country to the brink of civil war.

Among those involved in sectarian violence were the Shiite Mahdi Army, a militia loyal to radical cleric Muqtada al-Sadr, as well as gangs of al-Qaida-linked Sunni insurgents trying to drive out U.S. troops. Another Shiite group, the Iranian-linked Badr Brigades, was suspected of assassinating Saddam-linked army officers and officials of his Baath Party, targeting Shiites and Sunnis alike.

Iraq's Human Rights Ministry says about 70,000 Iraqis have been killed since 2003 and an additional 15,000 are missing and presumed dead. In a sign of the slow pace of digging up the blood-drenched past, authorities received tips about 76 locations where bodies might have been buried, but retrieved only three dozen bodies in six areas, said Kamil Ameen, a senior ministry official.

Prosecutors say al-Hashemi and his son-in-law, Ahmed Qahtan, ran death squads between 2005 and 2011, using a troupe of dozens of bodyguards to carry out bombings and shootings that targeted, among others, Shiite Muslim pilgrims and government officials.

The pair face 150 separate charges, but are currently standing trial only for alleged roles in three killings — of a lawyer, an Interior Ministry official and a member of the security forces. Al-Hashemi has denied wrongdoing.

The head of a human rights group in Iraq, speaking on condition of anonymity for fear of retribution, said he believes the government is trying to pin most of the blame for the sectarian violence on Sunnis.

"I am not defending al-Hashemi as I believe almost all politicians were involved in the killings of Iraqis in the past years, and their hands are stained with the blood of the Iraqi people," he said. "All Iraqis know that."

Joost Hiltermann of the International Crisis Group think tank said politics loom large in the case.

"Nobody is investigating anything. This is a file pulled out of the drawer," Hiltermann said of the al-Hashemi case. "The charges could have a basis, but there is no independent way of determining that" because Iraq lacks a functioning judiciary.

Hiltermann added that such charges "can be brought against any number of people on all sides."

Among those walking free is al-Sadr, whose support is key to al-Maliki's continued rule. Sadrists command 40 seats in the 325-member parliament and are part of an unwieldy ruling coalition that also includes the Sunni-dominated Iraqiya bloc and Kurdish groups.

Al-Sadr has sided with Sunni and Kurd politicians in a recent attempt to unseat al-Maliki, accused by his coalition partners of monopolizing power. But the cleric is also under intense pressure from his Iranian mentors not to topple the government.

Any legal action against al-Sadr would surely disrupt al-Maliki's efforts to keep him in the fold.

Al-Sadr was able in the past to leverage his political clout to avoid prosecution. Several years ago, an arrest warrant was issued for al-Sadr and two aides in the 2003 killing of a Shiite cleric who was hacked to death by a mob. Legal proceedings were suspended in 2004, as part of a deal to end fighting between al-Sadr's militiamen and U.S. troops in the southern city of Najaf.

A former commander of the Badr Brigades, Hadi al-Amiri, now serves as Transport Minister.

Al-Hashemi's defense team contends testimony against him was obtained through coercion. His co-defendants include more than 70 former aides and bodyguards, several of whom have testified for the prosecution. One bodyguard died in custody; the defense says he was tortured, while the government insists he died from kidney failure.

In three hearings so far, several bodyguards told the three-judge panel they were usually approached by al-Hashemi's son-in-law and asked to carry out attacks. They said that on occasion, al-Hashemi thanked them afterward and paid them.

The defense walked out of the second hearing after the court denied a request to obtain evidence that lawyers argued could exonerate the defendants, including the son-in-law's phone records. In the third hearing last week, defense lawyers sat among fewer than two dozen spectators and only approached the court once, to request that Iraq's president be called as a character witness.

The next hearing is set for June 19. Justice Ministry officials did not provide figures on trials against others involved in post-war sectarian attacks.