[shkkmo]

Leniency during sentencing is not effectively the same as plea bargaining at all. A plea deal comes from threats and fear, a lenient sentence handed down by a judge comes from remorse and judgment. Lenient sentences can come without a guilty plea anf a guilty plea doesn't guarantee leniency. The incentives are entirely different.

[simplestats]

The incentives are identical, less jail time. The fact that one is guaranteed deal while one is a standard sentencing practice is a distinction without a difference. The effect will be the same, innocent people "admitting" guilt. In Japan, plea bargains were illegal until recently. Yet standard police behavior when arresting someone was to notify them how much more lenient the system wold be on them if they admited guilt. And they were just stating facts about how the system works, not guaranteeing you anything... and racking up a 99.9% conviction rate. A lawyer in any country would tell you the same thing if your chances didn't look good.

[shkkmo]

The incentives for the judge and for the prosecutor are very different, though it sounds like the incentives for the police in Japan might be similar.