Information in Karel Sroubek's case file already showed that he should never have been allowed into New Zealand in the first place, but the Immigration Minister didn't use it in his original decision because he wasn't looking for it.
Iain Lees-Galloway announced today that he is reinstating Sroubek's deportation liability, because Sroubek's previous convictions in the Czech Republic made him an excluded person under the Immigration Act.
He said information about Sroubek's Czech convictions led to his new decision, which would see Sroubek deported after his drug-smuggling sentence and unable to return to New Zealand.
Sroubek's lawyer Paul Wick, QC, has confirmed he will appeal the decision.
Lees-Galloway now faces renewed scrutiny to explain why it wasn't already known that Sroubek was an excluded person, because his Czech convictions were contained in the 12-page summary of the original case file - released under the Official Information Act.
"Sroubek is wanted by Czech authorities for service of 54 months' imprisonment," the case file says, for attacking two police officers and a taxi driver, and for 2002 convictions for "disorderly conduct, damaging of another's property and attacking a law enforcement officer".
An excluded person is someone convicted and sentenced to jail for at least 12 months in the 10 years before arriving in New Zealand. Sroubek came to New Zealand in 2003.
Lees-Galloway said the Czech convictions were not relevant to his original decision to grant Sroubek residency.
Immigration officials told him that there were two matters for which Sroubek could be deported: Sroubek's conviction for importing MDMA, and his use of a false identity to come to New Zealand.
Lees-Galloway conceded that the information in the original case file was "potentially" enough to show that Sroubek was an excluded person, but he didn't think about that.
"That was not the question I was asked to consider ... I don't know every single detail of the Immigration Act.
"I didn't look at that and say 'Aha, he should be an excluded person!' ... I think it would be quite extraordinary to expect someone to think of all the possible questions that might be asked."
He said he had to make a decision based on the information officials had provided.
Asked if the officials should have considered whether Sroubek was an excluded person before giving him the file, Lees-Galloway said a review into the process should answer that question.
Lees-Galloway had initially granted Sroubek residency, but asked Immigration NZ to review the case after a court document emerged showing that Sroubek had returned to the Czech Republic in 2009.
This undermined Sroubek's claim that his life would be in danger if he were deported.
The review found new information, from Interpol, that led to today's decision that Sroubek is liable for deportation.
Lees-Galloway said the new information was additional to the Czech convictions in the original case file, but would not elaborate, citing the possibility of an appeal.
He conceded that public trust and confidence had been damaged, and the buck stopped with him.
He will not resign, however, but has apologised to Prime Minister Jacinda Ardern.
Ardern said she maintained confidence in Lees-Galloway, though he had made it clear he could have asked more questions.
"I think, now, obviously, he's issued a decision and now it's up to us to make sure we improve the way things are done in the future," Ardern said.
Lees-Galloway said he had immediately implemented changes so that he will receive a case file and take his time to digest it before meeting with officials.
His review, through the Ministry of Business, Innovation and Employment, will be carried out by Mike Heron QC.
Immigration NZ has also reviewing how it prepares case files, which will be completed in March.
During an urgent debate in the House, National's justice spokesman Mark Mitchell said Lees-Galloway should not be a minister.
"The country has lost faith and lost confidence in you."
But Lees-Galloway fought back, saying ministers had to rely on stringent information.
"Ministers cannot go charging around googling irrelevant information, hearsay, and unsubstantiated claims, and use those in making these types of decisions.
"It is essential that ministers rely on fact-based evidence provided to them by Immigration NZ."