Langridge said hundreds of hours of investigative work has gone into the case.
"We have spoken with a large number of people up until now and the investigation remains open and ongoing.
"It has been 12 months since her death.
"While Ms Harris' family continue to grieve for Tracey, we want to be able to provide them with closure."
He urged anyone with information about the death to contact police.
"Even if it seems small or insignificant, it could be a vital link to other pieces of information we already have.
"I ask anyone with information that may help us solve this case to speak to me as soon as possible."
Harris' son Jade Harris cut off his home detention bracelet in February last year, blaming the trauma of having his mother "murdered" two weeks earlier.
He was sentenced in the Masterton District Court to seven months' imprisonment after the judge cancelled his home detention sentence.
Langridge can be reached at Nelson Police station on 03 545 9679.
Alternatively information may be provided anonymously to Crimestoppers on 0800 555 111.