They're trying to show themselves as being a legit state, with a free and impartial judiciary. By making the girls disappear, it would have perpetuated the notion that they were just a chip off the old state's block.
Putin coming out and stating that he hopes the courts are lenient with them, allows the courts to then dish out a meaty sentence and then the state can turn around and say, "hey, look at how our legal system is independent of the president".
As I say, it was a blinder by him. It avoids all the kerfuffling that Ukraine is seeing over Tymoshenko's incarceration.
