Omar Waraich: Another attack adds to the pile of unsolved cases

There is now an established pattern that follows terrorist attacks in Pakistan. The grim details are beamed around the world and as Pakistanis respond with a mixture of shock, fear and anger, the world asks how much deeper the country can plunge. The government denies glaring security and intelligence failures. Ministers insist they are pursuing strong leads and vow to bring the perpetrators to justice.

Yet once emotions have subsided and the media's focus shifted elsewhere, there has been no closure. It is still not known who assassinated the former prime minister Benazir Bhutto. There are confusing claims about the authors of the devastating attack on the Marriott Hotel in Islamabad last year. And as authorities flounder in their pursuit of the gunmen who mounted the "3/3" attack on the Sri Lankan team in Lahore, there are fears that another atrocity will pass unpunished.

"I don't think we will ever find out who did this," said Ayesha Siddiqa, a security and military analyst. "Confusion reigns at the main policy-making level. There is no consensus on how to deal with this threat. There are bureaucratic inefficiencies. There is a fear of these militant organisations. And there is the argument that the government is complicit."

In some cases, suspects have been rounded up but never brought before court. These relatively low-level operators are prized by investigators as rich sources of information. "They are very reluctant to bring them to court," says Talat Hussain, a journalist who has covered investigations. "While in custody, they are seen as a route to the larger terrorist network."

Many suspects are never caught. A sclerotic bureaucracy often fails to pursue cases to their conclusion. "When it comes to perpetrators of most terrorist attacks, the cases are open, but the ledger is incomplete," Hussain says. "And much of the investigation is done by military intelligence agencies who shun the public profile."

Those who assassinated Ms Bhutto 16 months ago are still at large. At a gathering to mark the first anniversary of her death, her supporters taunted her widower, President Asif Ali Zardari, with chants of: "BB, we are ashamed, your killers are still alive."

A number of other investigations have been associated with allegations of appeasement and even official complicity.

During the siege of the radical Red Mosque in Islamabad, Hussain says, "people who were connected to major terrorist groups were allowed to go scot free" through a deal with the government of General Pervez Musharraf.

When the former military ruler imposed a state of emergency in November 2007, 25 militants from Swat were released as part of a deal while lawyers and democratic politicians were being arrested.

Despite its public disavowal of supporting militant groups, there are lingering suspicions that serving and retired members of military intelligence maintain links with their former clients in the jihadist underworld.

Last year, the links came to light when a retired army officer was arrested and accused of plotting a suicide attack on an air force bus.

Security failures: Suicide killers

December 2007: Former prime minister Benazir Bhutto, pictured, is among about 20 people killed in a shooting and suicide attack during an election rally in Rawalpindi. Scotland Yard detectives were later asked by General Pervez Musharraf, then president, to investigate the attack.

September 2008: A total of 57 people are killed when a suicide bomber drives a truck full of explosives into the front gates of the Marriott Hotel in Islamabad. A month later, four men suspected of "indirect involvement" in the attack are arrested. None has been put on trial and the investigation is said to be "floundering".