Her crying frustrated her teenage dad, who shook her so badly she died from her injuries. Police had their eye on Wichman after Teegan died in 2009 but needed proof. So they launched an elaborate five-month "Mr Big" operation to draw a confession from him.
Jimmy Ellingham looks at how they did it.
Three years after 11-month old Teegan Tairoa-Wichman died, and after three interviews with her father Tawera Wichman, police concluded they still didn't have enough to prosecute him for her death, an opinion backed by the Crown solicitor's office.
So they came up with a plan.
The brainchild of the Royal Canadian Mounted Police, the Mr Big covert operation is used worldwide by police for cases they can't crack despite having a strong suspect.
They gain a person's trust, include them in an apparently criminal outfit and then elicit information about the major crime under investigation. Various scenarios are often designed with input from a clinical psychologist, as was the case for Wichman.
His Mr Big trap was set in December 2012 when he was 21 and over the next five months he was sucked in over 21 carefully staged scenarios.
He and Teegan's mother Tamara Tairoa, who met at their Upper Hutt secondary school in December 2007, had moved from Wellington after their daughter's death and were living at his father's place in Auckland with their two remaining children.
They'd had Teegan and her twin when Wichman was only 17 and Tairoa 16, and another child when they were still teenagers.
Wichman was working for his old man.
An undercover cop knocked on their door and convinced Wichman to complete a survey. He did so and "won" a 4WD and go-carting holiday to Rotorua.
On the February 2013 adventure with other "prize winners", who were actually police officers, Wichman met and became friendly with a guy he knew as Ben.
Ben recruited him to work repossessing vehicles and other "stand-over" debt collections for his boss, the Mr Big, Scott.
Ben told Wichman the organisation "engaged in criminal activities" but lived by the creed of "professionalism, respect, trust, loyalty and honesty".
Wichman, a criminal freshman, became more involved with his new mates, undertaking what he thought were criminal acts such as obtaining a false passport, a burglary where guns were stolen and selling the "stolen" guns and cannabis.
Included in the staged scenarios was an exchange of weed and guns for diamonds and cash, with men posing as triad gang members.
One time, Wichman was involved in delivering cannabis at a country airfield late at night.
He was also asked to count large sums of apparently stolen money.
During this time, Wichman also dealt with CJ, whom he thought was a corrupt cop. These dealings involved Scott and CJ "sorting out" sexual offending charges against Craig, another member of the gang.
In another incident, to reinforce protocol, Wichman witnessed a staged dismissal from the group by a member who had a "bad attitude" and "asked too many questions".
For all his work, Wichman bagged $2600 but during the last month of the Mr Big operation, Wichman's telephone calls with his dad and Teegan's mother were bugged.
A few months after the initial meeting, Wichman's mum was told by police there would be an inquest into Teegan's death, deliberate and crucial timing to make sure his daughter was at the forefront of their target's mind.
Wichman told Tairoa he thought he'd face prosecution.
On May 2, 2013, it all came to a head for Wichman, when he was interviewed by Scott, the boss.
In a secretly recorded interview in a Dunedin apartment - the southern location carefully chosen to isolate Wichman - Scott told Wichman the gang lived by rules valuing honesty and trust.
He told him he knew about his troubles with the police but that he could fix the problem and didn't care what Wichman had done.
He wanted Wichman on gang duty permanently but needed reassurances before a big job in Melbourne.
He was told there was no pressure to stay if he didn't want to but bent cop CJ had checked him out and found something about the "death of a kid".
Wichman started to, slowly, come clean, although at first he stuck to the story he'd told police - that he shook the child because she had had a choking fit and stopped breathing and he was trying to resuscitate her.
"My daughter got um sick, she, she got hurt, you know. Someone hurt her and ah yeah ah, the night that um I found out about it all, um, I was looking after the kids and ah she, she stopped breathing right next to me and I had to perform CPR on her."
He told Scott about CYF involvement with the twins before the discussion moved to rugby league and other people.
Then came the clincher. Scott again spoke about the organisation's values and said if Wichman made any mistakes, he needed to say.
But he said Wichman didn't have to if he wasn't comfortable.
As the conversation slowly developed, Scott said he had a medical report about Teegan that CJ gave him.
Wichman slowly opened up, admitting giving Teegan a "pretty good shake" on March 4, 2009, and one time before that. He said he did so because she was crying and he couldn't comfort her.
Wichman continued, saying he'd not been totally frank to the police. He was upset and Scott gave him a tissue.
Wichman apologised for lying to Scott initially and thanked him for the chance to confide.
Wichman was eventually charged with his daughter's manslaughter, appearing in court in 2013.
Police had their confession but Wichman wasn't going to accept what happened and in round after round of legal wrangling, sought to have the evidence obtained in the Mr Big sting ruled inadmissible.
In a court hearing, Wichman again changed his story, saying everything he told Scott was a "complete act".
At a pre-trial hearing Wichman said he thought he'd be fired if he didn't say what Scott wanted to hear and he was concerned about "safety issues" in Dunedin.
A Supreme Court judgment from Justices Terence Arnold, Mark O'Regan and William Young says Wichman was "under some pressure to confess".
"Full membership of the organisation was attractive to him in terms of lifestyle and economic benefit. He could not, however, attain full membership unless he passed the interview."
The judges said Scott made clear he thought Wichman assaulted his daughter and he might have thought anything less than a confession would see him kicked out of the gang, the judgment said.
Wichman also thought he would likely face prosecution anyway and saw his confession to Scott as a means of helping him avoid this, the judges said.
"It is also possible that he was affected by some more subtle pressures resulting from a wish to fit into the ethos of the new organisation and a desire to maintain his association with its members. He was led to believe that a confession would be cost-free."
But, crucially, the Mr Big operation was never threatening or violent and Wichman was told he didn't have to discuss his daughter's death if he didn't want to - that would simply mean he left the gang.
In the tapped phone calls Wichman never gave any indication he felt intimidated.
The Supreme Court ruled the Mr Big evidence could be used in court but it was a split decision.
Chief Justice Dame Sian Elias was against allowing it, saying: "There is much in a scenario technique that is unexceptional and may properly be deployed in a police investigation.
"It is its culmination in an interrogation without procedural safeguards against the background of a reality constructed by state deception that I consider to be unacceptable."
Catching out Mr Dumb
Mr Big operations have been used in New Zealand in five other matters.
This year the intricacies of the technique were revealed in the undercover operation to catch double murderer Kamal Reddy, who is serving at least 21 years in jail for strangling partner Pakeeza Yusuf and her 3-year-old daughter Jojo Kalim.
The pair were slain in late 2006 or early 2007 but it was only a confession by Reddy in October 2014 that led to his conviction.
As with Wichman, undercover cops gained Reddy's trust, drew him into an organised criminal syndicate and over the course of two interviews he admitted killing the pair and said their bodies were hidden under a North Shore motorway bridge.
"These guys must be so dumb," Canterbury University criminologist Greg Newbold told NZME when asked how Wichman and Reddy got sucked into opening up.
"I think the police should be applauded for their ingenuity and their terrific acting and planning. They put a lot of work into these things to get a result."
Newbold said such operations were "absolutely ethical".
"You're catching these fools by their own stupidity. I think it's really good," he said.
"They think they've found a bunch of soul-mates who are going to be best friends and who are going to help them earn a lot of money.
"They know the ethics of the groups and they trust that they are not going to blow the whistle."
Sometimes the targets might think confessions earn "kudos" with their new criminal mates, although that's unlikely in Wichman's case.
"I think that he thought they thought he was pretty cool."
Teegan Tairoa-Wichman assaulted by her father and taken to hospital
March 6 and March 11, 2009: Police interview Wichman, who admits shaking Teegan in an effort to resuscitate her.
September 8, 2009: Teegan dies in Hutt Hospital.
November 5, 2009: Wichman is again interviewed by police but this time doesn't want to say anything.
April 2012: Police concluded they didn't have enough to prosecute Wichman.
December 2012: Police start "Mr Big" technique to try and get a confession, starting with knocking on Wichman's door and getting him to fill out a survey, before telling him he's won a trip away. Over the next five months he was sucked in over 21 carefully staged scenarios.
February 2013: Wichman takes trip with other "prize winners" and meets a handful of undercover cops and undertook what he thought were criminal acts.
May 2, 2013: Wichman confesses to "Mr Big" and police arrest and charge him with manslaughter.
July 21, 2016: Wichman sentenced to three years and 10 months in jail.
Mr Big undercover technique
• The suspect is introduced to an undercover officer who spends time gaining his trust.
• He/she is invited to participate in staged criminal activities with the officer.
• It is designed to show he/she is working with a successful criminal organisation.
• The suspect is introduced to other undercover officers, posing as gang members or associates, throughout the operation.
• A "big boss" at the head of the organisation eventually has the role of inducing the truth from the suspect.
• The technique originated in Canada and has been used in Australia too.
• It must be authorised at the most senior levels within the police force and must only be used as "a last resort" when other investigative options have been exhausted.