One way you can see that the Sadducees were in control of the Sanhedrin is that in the reported trial of Jesus, there was almost no law that was not broken. The was not one single legal procedure that was not flaunted and broken during that trial.
Just one example: saying that one is the son of God is not blasphemy. Blasphemy has a legal definition which is: May "Jose strike Jose." Jose here is used to stand for the Name of God because during the trial you don't want to keep repeating the phrase. For someone to claim they are the son of God is not unusual because we say this three times a day in every Shmoneh Esra and this comes up very often in the prayer book. We all call God "Our Father" more times than I can count. Doing so is not blasphemy though it might have been to the Sadducee.
Some problems with the trial: At night. Even if a person does a sin that gets the death penalty which did not exist in that case still you need two witness to warn the person right before he does the sin. That is to tell him both the sin and from what verse it comes from and the penalty. None of this existed then There is a whole tractate in the Talmud about this one aspect of laws. It is not a trivial detail. I could go on but you can just open up a tractate Sanhedrin and Makot and see it all for yourself.