Adam Kearns, 18, spent 18 days in jail, set up by his other who sent herself violent death threat texts and pretended they came from him.
Mr Kearns was arrested, denied bail, and spent 18 days in jail for a crime he didn't do.
Milner was jailed in August last year for two years and eight months for perverting the course of justice in framing her son.
Mr Kearns' lawyer Kerry Cook confirmed he is seeking $60,000 in damages from Milner.
Mr Cook said his client is suing over a "malicious prosecution ... that she knew to be false''.
"I've got instructions to file a claim against Milner for the time Adam wrongly spent in jail,'' Mr Cook said.
A letter of demand was served on Milner during her High Court murder trial, he said.
Milner had yet to respond.
Problems with investigation - Police
A senior police officer has acknowledged significant flaws in the way the death of Black Widow victim Phil Nisbet was first investigated.
Police initially ruled the 47-year-old's death in 2009 was a suicide. A homicide probe - which ultimately led to his wife Helen Milner being found guilty of murder today - was launched only after a coroner raised concerns.
This afternoon Canterbury Police district investigations manager Detective Inspector Tom Fitzgerald confirmed to APNZ that the first investigation was badly flawed.
"It wasn't treated as a homicide. Unfortunately, that was the mistake that was made," he said.
"Therefore all those parts of an investigation which we would expect, with interviews, exhibit handling and everything that goes with that to a standard I would expect, weren't conducted.
"It was treated as an unexplained death and it wasn't given the normal investigation we would expect of a homicide investigation. That's where it starts and stops really. Because of that, the investigation wasn't done as it should have."
Mr Fitzgerald expressed concern that senior officers did not listen to worries raised by the first two officers on the scene, who had suspicions over how things were playing out.
They thought Milner's hysterical actions amounted to "acting" and found it too "convenient" that she switched on her cellphone in front of them to receive a supposed suicide text from Mr Nisbet.
"The initial investigating officers didn't treat it as a homicide. Taking into account what was said by those that first attended, that should have certainly pushed them in that direction. Unfortunately in this case, it didn't happen.
"There were a number of points that were not done correctly."
An internal investigation was carried out and the Independent Police Conduct Authority was brought in.
The IPCA did not take things further, but the first officers in charge of the investigation - detectives Richard Prosser and Scott Anderson - have been "counselled over their treatment" of the initial inquiry, Mr Fitzgerald confirmed.
"They were spoken to in respect of their shortcomings and everything was made clear as to what those shortcomings were."
A spokeswoman for the IPCA confirmed a complaint was received in August this year relating to "an allegation of an inadequate police investigation".
"Because police had already investigated the substance of the complaint and had effectively upheld it, and taken disciplinary action against the officers involved, the IPCA referred the matter back to police to engage with the complainant to resolve the matter," the IPCA said today.
