"The process has been gradual, but in the last month or so the matter's come to a head and we have briefed forensic experts."
One of those experts is believed to be forensic scientist Dr Anna Sandiford, who worked as an expert witness in David Bain's retrial, was employed to review the evidence before Teina Pora's Privy Council appeal and will give evidence at Mark Lundy's retrial next year.
The forensic experts will investigate what Mr Tennet claims were "severe deficiencies" in Reid's cases.
The legal aid will also fund an overall review of other areas of Reid's case including "the fairness of the trials and whether he did either of the offences".
"This matter has been through two experienced appeals lawyers, both of whom started the legal aid process. The grant, in theory, was given some time ago," Mr Tennet said.
"The reason we got legal aid was to bring a second appeal to the Court of Appeal. These things are difficult to do at the best of times and they require a lot of work to get them to the stage where they are arguable.
"I am very confident in what we're doing and I expect that confidence to remain when I've seen the forensic material.
"We'll be assembling evidence and we will be assembling various submissions to support the application."
Mr Tennet said he expected to file the application to appeal "in the early months of next year".
Reid's former lawyer, Davina Murray, was convicted and sentenced to 50 hours' community work last October and removed from the Law Society's register after being found guilty of smuggling an iPhone, cigarettes and a lighter to Reid at Mt Eden Prison.
During her trial, the Crown said Murray and Reid's relationship went beyond that of lawyer-client.
She also appealed against her conviction and sentence, but it too was dismissed.