The 38-year-old died last month in a care facility almost 9 years after he was attacked by a group of up to 15 people at a BBQ at a house on the Chapel Road on July 15th 2006.
Since Paul's death, one man has been charged with his murder. Three other people arrested as part of the renewed investigation are on police bail pending further enquiries.
Police have now arrested a 46-year-old in the Fountain area and a 27-year-old in the Waterside.
A property is also being searched in the Waterside.
The suspects had been taken to Strand Road police station for questioning.