Why did Kasab confess??

It's difficult to believe that the confession is due to remorse, change of heart or an inability to go through the distressing, prolonged trial.

Let us no mistake. Kasab is a highly trained, motivated terrorist. Terrorists , specially terrorist killers have no  shame, no sensitivity, no regrets. Any human being who has killed without a reason, on instructions, has no conscience or soul anymore. No matter what human rights activists may say, there is no place for them in civilised society. They have to be executed but it has to be shown that they have been punished not on the spur of the moment, but by deliberate judgment because they have broken all norms of social behaviour, because they have taken the most precious possession of a human being--his life--and without any warning, notice or  provocation.

So why did he confess, knowing fully well that he has merely hastened his own death?

There are two reasons.

By doing it, he wants to take the slight chance that he may just get a Life imprisonment. Though this possibility is practically nonexistent, there was no harm in trying. If he could escape with such a judgment, there is a possibility he could just escape by an exchange with hijacked hostages or some Indian agent.

The more plausible reason is that he was instructed to do so by the Pakistan Government. there is a great battle waging in that country between civilised society which has a majority support and the power seeker nexus between terrorist groups like the ISI, Taliban, Lashkar etc.

This struggle changes hourly or daily. Kasab has implicated the Lashkar group. This will make it easier for the present government to go after the terrorist groups by arresting them and probably convicting them . However, these groups will use all their influence to stop this pathway. That is why, the trials will be delayed, there will be backpedalling, releases, withdrawals. Kasab's confession gives the government some cards to play in this ongoing battle. That is why immediately after the Joint Declaration at Egypt and the discussions before that, a gameplan has been activated between the two governments. This gameplan includes Kasab's confession as the first pawn move.

With Sarabjit being used as a counterpoint to Afzal, there is an effective delay to the execution of both of them. One wonders whether some other counterpoint is being prepared for Kasab and thereby causing a delay in  his execution ?? For execution is the only verdict possible for Kasab....