Complex sentence: Unbeknownst to his human monitors, RoboCop still retains memories of his life as Murphy, including brief glimpses of his wife and son, and the action of spinning his gun before holstering it, a trick Murphy had done for his son.
Split into simpler sentences: Unbeknownst to his human monitors, RoboCop still retains memories of his life as Murphy, including brief glimpses of his wife and son. A particular habit Murphy retains is the action of spinning his gun before holstering it, a trick Murphy had done for his son.