He said the inquiries involved separate individuals and separate events - but the inquiries have limited features in common.
"To what extent there is genuine commonality in the issues that I will need to determine in each inquiry, will not be known until the conclusion of each inquest."
He said there's a risk in the perception of commonality in the circumstances, and a level of fault or blame, presumed on the basis of perceived commonality, before the inquiries have been determined.
A coronial spokesperson said there could be joint inquests, or inquests could be clustered together, to help speed up the process when multiple people have died at the same time or in similar circumstances.
Clusters have occurred before in Coroners Courts, including with quad-bikes in 2013.
Three quad-bike deaths over eight weeks in Northland were looked at by a coroner to see if there were any common links that could help prevent similar future fatalities.
Eight inquiries were also held in Rotorua into deaths between March 2012 and November 2013, that raised important issues about forestry safety.
Coroner Wallace Bain said the inquests were grouped together deliberately because of the commonality of them all being in the forestry industry, despite differing circumstances relating to their deaths.
Coroner Bain gave no specific recommendations in a combined decision but praised industry efforts to reform the sector and noted they needed to stay alert to dangers.
In the months after the five Wellington killings currently being investigated, a review was held by Capital and Coast District Health Board, into its mental health services.
It concluded improvements could be made in several areas, including developing a single electronic record for mental health patients and clarity in client recovery plans.
Nigel Fairley, Capital and Coast DHB General Manager of Mental Health, Addictions and Intellectual Disability Services, said they had since implemented all the recommended improvements.
They were largely addressed with the implementation of the "Client Pathway" which is a single digital clinical record for a client's engagement with services, he said.
An independent mental health victim advocate supported the deaths being looked at around the same time by the coroner, in case any similarities are found.
Graeme Moyle's brother was killed in 2007 by a man who was released from an Auckland mental health unit months before.
Since then, he's advocated for an independent investigation authority, to look into cases where homicides are caused by someone with mental health-related problems.
A similar model exists in the United Kingdom, where killings or suicides involving people who have been in mental health care for up to 12 months prior are looked at by an independent board.
He said the deaths being looked at by the coroner were a "great idea".
"My only concern is that the coroners don't have any teeth. They come out with recommendations but the DHBs can just give them the finger and say we're not going to implement it.
"It's good to get recommendations but they still have to be implemented to make any changes."
