Complex sentence: John Harding, who had a previous conviction for perjury and was being detained in prison at the time, "at the Governor's pleasure", testified that Ross had confided in him in prison, and had admitted his guilt.
Split into simpler sentences: John Harding, who had a previous conviction for perjury, was being detained in prison at the time, "at the Governor's pleasure". He testified that Ross had confided in him in prison, and had admitted his guilt.