Keeping the alleged plotters in jail will require unprecedented investigative cooperation across a border mined with distrust and suspicion, and the onus has shifted to India.
Pakistani authorities say they will prosecute in their own courts anyone linked to the three-day siege in Mumbai that left 164 dead - they just need the proof.
"Our own investigations cannot proceed beyond a certain point without provision of credible information and evidence," said Pakistan's Foreign Minister Shah Mehmood Qureshi.
But Indian Foreign Minister Pranab Mukherjee said it was too early to share any of what investigators say is ironclad evidence tying the attacks to Pakistani soil. According to India, the 10 gunmen were from Pakistan, as were the handlers, masterminds, weapons, training camps and financing.
"Whatever evidence we have, we can make available," Mukherjee told Indian news channel CNN-IBN in an interview to be broadcast Sunday. "We are also investigating. We have not come to any conclusion. Therefore, at this juncture, perhaps it would be premature to share the evidence."
It remains uncertain how much evidence, if any, India will actually provide.
India finds itself in the awkward position of having to investigate terrorist attacks hand-in-hand with its longtime nemesis. The two countries have fought three wars against each other since independence. Despite a peace process that began in 2004, tensions remain high.
"India grits its teeth and says 'They don't have to like us, we don't have to like them but ... we have to go through the process,"' said C. Uday Bhaskar, a prominent defense analyst in New Delhi.
Their tense relations were evident Saturday as Islamabad said Indian aircraft violated Pakistani airspace - crossing into Pakistan-controlled Kashmir and over the eastern city of Lahore - before being chased back over the border.
India's air force has told Islamabad the incursion was "inadvertent," Pakistan Information Minister Sherry Rehman said.
Indian officials could not immediately be reached for comment.
Much of India's information comes from Mohammed Ajmal Kasab, the lone captured gunman. Through repeated interrogations, he has said he was trained by Lashkar-e-Taiba, a banned Pakistan-based militant group, and revealed key details such as names of fellow plotters and locations of camps.
Islamabad has refused to even acknowledge Kasab is Pakistani, complaining it has had to rely on news reports for information.
Most recently, a Pakistani newspaper, Dawn, tracked down Kasab's family in the village of Faridkot - his hometown according to Indian investigators - and said the suspect's father had identified his son from photographs of the gunmen.
Pakistan has taken action in recent days, closing 65 offices of a charity linked to militants, putting the charity's prominent founder under house arrest and arresting senior Lashkar leaders, including the attacks' suspected mastermind.
But Mukherjee said India was still not satisfied, and he wanted Pakistan to ensure banned groups don't "reappear in their new name with the new signboards but with the same old faces."
Pakistan outlawed Lashkar in 2002 under pressure from the United States, but many say the group resurfaced under the umbrella of Jamaat-ud-Dawa, a charity group the United Nations this week labeled a terrorist outfit. Pakistan began shutting the group's offices late Thursday and ordered its assets frozen.
India has traced previous terrorist attacks back to Pakistan, but animosity and distrust at the time ruined any hopes for cooperation.
After the 1993 Mumbai blasts that killed 257, India provided evidence of Pakistani complicity - which Islamabad rejected as "fabricated," said Bhaskar.
"Pakistan has never accepted culpability of its own people or handed over anyone," he said.
This time may be different.
For starters, evidence collected by India from Kasab, as well as recovered phones and forensic evidence, may be too strong to dismiss, analysts say.
The siege also stands out because 26 foreigners were killed, which has brought investigative help from other countries and international pressure that makes it harder for Islamabad to avoid taking real action.
But India's probe also includes intelligence apparently gleaned through top-secret eavesdropping against Pakistan, which authorities will be loath to share.
In September, India's foreign intelligence agency intercepted telephone conversations apparently coming out of Pakistan that discussed possible attacks against Mumbai hotels, according to a government official who spoke on condition of anonymity because of the sensitive matter.
India will almost certainly not disclose details of its espionage work to Pakistan, the program's main target.
While Indian investigators have raised possible links between the militants and Pakistan's spy service, Mukherjee has been very careful not to accuse Pakistan's government of complicity in the siege.
"That is why, repeatedly, I said 'elements from Pakistan"' were responsible for the attacks, he said. "That is a phrase I have used meticulously. I would not like to be more specific unless definitive conclusion is arrived at by the investigating agencies."
