Author of Acts (Luke): Mistake of Ignorance (Geza Vermes)
The Acts of the Apostles goes even further than Jospehus and the Gospels when it turns the Sadducees into complete materialists who denied not only the resurrection of the dead, but also the existence of angels and spirits (Acts 23:8). However, this exaggeration should probably be blamed more on the Gentile Luke’s unfamiliarity with Palestinian Jewish thought than on the Sadducees, for angels are commonly mentioned in the Bible and the Sadducees were sticklers for the letter of the scripture. 
Luke wrote the Gospel of Luke and the Book of Acts* – both of which, Christians believe to be inspired by God – yet, Luke seems to have blundered through ignorance or exaggeration. One must ask, if the author could blunder to this extent then what other mistakes did he make. And if he was making inaccurate statements then how can one sincerely believe he was inspired by the Holy Spirit?
This is another problematic issue for our Christian friends to ponder upon. Previously, we have seen that the Christian belief that the Holy Spirit guides them in scripture is problematic for them and now we are seeing their belief of the evangelists and authors of the Bible being inspired by the Holy Spirit (whom Trinitarian Christians believe to be God) as problematic too.
You decide if this is an error on the part of Luke!
*Some scholars attribute to Luke the third Gospel and the Acts of the Apostles, which is clearly meant to be read as a sequel to the Gospel account. Other scholars question Luke's authorship of these books [http://en.wikipedia.org/wiki/Luke_the_Evangelist]
 The Resurrection, Geza Vermes, Penguin Books, 2008, pg. 48
What Every Christian Should Know About the New Testament