"Whilst limited information is known about his index offending, the following factors were implicated: perceived sexual rejection, ruminations upon revenge, positive affect associated with inflicting pain and distress, and disinhibition through alcohol intoxication.
"Based on his past behaviour, should he reoffend Mr Watson may display a high level of callousness and employ significant efforts to evade detection."
The Parole Board noted that Watson was unwilling to participate in rehabilitation programmes, because he maintains his innocence, but was willing to have one-on-one psychological counselling.
The decision also outlined his "uneven behaviour" in prison which had improved recently but included numerous incidents involving other prisoners, staff and disregard for rules.
While serving his sentence, Watson was found guilty of four incidents of misconduct - including assaulting a fellow inmate until he was unconscious - and two positive drug tests in 2001 and 2002.
He has recently appeared in the High Court at Christchurch where a judge overturned the decision of the Corrections' Department to prevent an interview with journalist Mike White.
Watson and a number of supporters maintain he did not commit the murders, but the Parole Board said it not take into account guilt or innocence but the crimes on which he is convicted of.
The Court of Appeal has previously dismissed his bid to overturn the convictions, while the Privy Council did not grant Watson leave to present his case.
An application to the Governor-General for the Royal Prerogative of Mercy was also declined.
Watson will be seen by the Parole Board in 12 months' time.
