The head of an undercover police sting involving a British Columbia terror suspect says he "absolutely" urged his officers to consider their suspect developmentally delayed.

RCMP Sgt. Bill Kalkat, has told B.C. Supreme Court that police scenarios were designed to take John Nuttall's mental capacity into account.

Nuttall and his wife Amanda Korody were found guilty last June of plotting to blow up the B.C. legislature on Canada Day 2013.

Their lawyers are arguing that police manipulated the couple into attempting to carry out a terrorist act.

Early in the undercover operation, an officer gave Nuttall $200 to transport an unmarked package to a transit-station locker.

Kalkat says Nuttall was told that the package's contents weren't illegal but admits it would have been possible to question the operation as illegitimate.