Do you have sources for that? http://hakusyo1.moj.go.jp/en/64/nfm/n_64_2_2_2_2_0.html#tabl... has some data about the number of cases that are prosecuted and that's way lower than 99.98%, but that's not limited to people interrogated.

But indeed, if you look at the data for cases that go to court, the conviction rate is high. http://hakusyo1.moj.go.jp/en/64/nfm/n_64_2_2_3_1_0.html

But that was my point in GP.