|Family||Jo Gage (daughter)|
|Status||Imprisoned for life|
|First Appearance||"Blind Spot"|
Declan Gage was one of the first criminal profilers and a former employee of the FBI.
Currently, Gage is a very unstable man, whose word and opinions cannot be taken seriously, as they are more than likely products of paranoid delusions. As well as being the profiling mentor to Goren, his studies were once considered very reliable and respected among his colleagues, but a mental breakdown changed all of that. Goren is the only person who puts any stock in his opinions.
He mistreated his own daughter, Jo Gage, because he wished he could have had a son, which he saw in Goren. This turned her in time into a serial killer, who murdered three people in order to just get her father's attention. When Jo was exposed, he was only happy that he had helped in the catching of a serial killer. This behavior led to a falling-out with Goren.
Later, Gage became closer to Goren, though only in a limited way, when Goren found out that his real father was Mark Ford Brady and had no one to turn to about it. It happened during the funeral of Goren's mother, where he also appeared. There, Declan also found out how messed up his private life had become. Based on this knowledge, Gage teams up with Nicole Wallace to kill Frank Goren. After that, he also kills her in order to free Goren of the three people in Goren's life he viewed as poison, including himself. Jo's refusal to see him again was the trigger of this. After that, Gage frames Goren for the murders to make him fight back and even sets himself up as one of Nicole's victims to help sell the story. He is eventually exposed and arrested for the murders.
Gage was tried and convicted of all murder charges against him (including Nicole's) and was sentenced to life imprisonment without parole in maximum security.