In the senate trial, Michael is answering a series of questions, many of which have to do with the events of the first film. Now follow me. The senator asks him if he killed Sollozzo in 1947 and ordered the hits of the 5 families in 1950. In the first film, Tom Hagen, before Michael kills Sollozzo, comments "this is almost 1946!" Would Michael wait more than a year to do the killing. The 5 families slaughter takes place after Don Corleone's death, which is way after the death of Sonny. The Don's headstone says 1955. Right before Sonny is shot, you can hear a baseball game. Listen closely, it is the famous "shot heard 'round the world" which took place in October 1951. So Michael wasn't telling a complete lie. The events are correct, but the timeline does not jive.