Mancini was on loan at AC Milan from Inter Milan in one of those typically weird Italian loan moves that seem really dodgy. He went to a party hosted by Ronaldinho back in December last year. Here he met a young Brazilian girl and we can only speculate as to what happened next but whatever happened was clearly not consensual.
The evidence must have been overwhelming for Mancini to be convicted. A footballer is in the papers pretty much every week these days being accused of a sexual assault but very rarely do they ever go to court, let alone get convicted. I imagine this is in no way a result of the millions of pounds they have to throw at any potential problem that comes their way.
Mancini, unfortunately for him but fortunately for the rest of us who don't go around raping girls, is not a good enough or famous enough sportsman to get away with such a crime (see Kobe Bryan -allegedly). I remember Mancini scoring some great goals for Roma and Inter, unfortunately for him the next time he scores it will be in the showers.