These perpetrators I knew from my old circuit and knew them to speak to (before I knew about them or afterwards when I felt obligated to) before they moved away or got DF'd.
1. I became aware of this one when was a teenager aged 16 through 19 who during that time abused younger boys sexually. This was 1980's. He was a pioneer and was DF'd when it came to light but no report was made to the police at the time. It was about 20 years later by one of the (now adult) victims and the police investigated it.
2. The next one was the high profile (in England) Michael Porter (from Somerset) case in 2007 - he was a late teen through mid twenties pioneer and MS when he perpetrated his acts of child abuse much earlier. Several of his victims were either too young to know what he did to them or too fearful to tell anyone. Eventually a victim, now an adult told him that if he didn't self report to the Police then he (the victim) would. Porter coughed to even the cases where the kids were too young to have remembered and he pleaded guilty. He got a suspended sentence but this was appealed and eventually he got sentenced to 18 months real jail time.
Porter had already left the area, married, become an elder and a bethelite before being exposed. He was in an English London flagship congregation and was service overseer on a body of elders which included some of the London Branch Committee. He got a public reproof and a District Overseer was sent to placate his home congregation when they wanted to know why he wasn't disfellowshipped.
I believe he has a child of his own who he is not permitted to have contact with unless supervised by social services! What a mess.
3. Another one was when I was an elder and we "inherited" a now dead paedo (twisted, self entitled bastard - hooray!) who had done jailtime and been sent to our town by the authorities. They told us that he was a paedo and needed watching. We informed "family heads" of his background; but several older sisters found out through the grapevine and "were incensed" at not being told. One who had been abused as a child DA'd over it.
So 3 plus others that I knew about in less detail from other JW's.