When L has Misa kidnapped (he's almost certainly not relying on regular judicial procedures, so it's a kidnapping, not an arrest), he instructs Watari to interrogate her but to keep her alive. And such clarification certainly isn't needed if torture is out of the question. Even more when Misa looses her memories of the death note, she specifically asks her kidnapper to kill her, because she can't take it anymore. So, was the honorable Japanese Task Force watching a video feed of their boss' son's girlfriend being tortured?
Highly likely. Even the way she was being held, permanently strapped down and blindfolded, for, what was it, 50 agonizing days, could be considered torture.
This is part of why I sympathized with Kira more than with those who were trying to catch him. Fact is, for all their noble rhetoric, they weren't so moral either. They were just as much "the end justifies the means" sorts of people as Kira was, just as willing to commit injustices within the framework of what they considered a just cause. Say what you will about Kira, but he didn't torture people for weeks on end; merely gave them a quick clean death.
"The comfort of the rich depends upon an abundant supply of the poor." - Voltaire
I lost sympathy when he killed that reporter who was on his trail. Plus he still killed them regardless of if it was long or slow, whilst L's crime was bad but not death.
Yeah i'm not saying he was perfect or anything, just that the police weren't all that much better. If Kira existed in real life I doubt i'd sympathize with him.
The people, and the people alone, are the motive force in the making of history. -Mao Zedong