Detective Garda Shane Curtis told John O'Kelly, prosecuting, that he examined two notebooks seized by members of the Garda Organised Crime Unit who raided Rattigan's cell in Portlaoise Prison on May 22, 2008.
He said the nature of entries replicated across one notebook, which contained details of weight categories, calories burned and times, suggested the book was a gym diary.
Det Garda Curtis said that a diary entry that read "block for six weeks" referred to the placement of Rattigan on the segregation block in Portlaoise Prison, as his own inquiries revealed that Rattigan was kept on the segregation block from December 3, 2007, through to January 14, 2008.
He agreed with Mr O'Kelly that one of the notebooks contained a long list of names such as "Dicko" "Brian" and "Crazy" followed by "half" and numbers such as "9", as well as an entry dated May 2, 2008, that read: "Rock sorted, the glove with McGyver."
Det Garda Curtis said that in his opinion the list was a drugs tick-list, detailing names and weights of drugs.
He told Mr O'Kelly he examined the other notebook found in Rattigan's cell and found that it also contained a drugs tick-list recording names pertinent to the investigation.
Rattigan (32), formerly of Cooley Road, Drimnagh, has denied possession of heroin and possession of the drug for sale or supply on Hughes Road South, Walkinstown, Dublin on May 21, 2008.
He has also denied possessing two mobile phones at Portlaoise Prison.
The trial continues.