That meant he got paid big bucks - at least $165,000 - and was able to prescribe medication to mental health patients.
Siddiqui wasable to print the original ABPN certificate, which was then passed to the relevant authorities, including the Medical Council of New Zealand, IMR- which is based in Australia - and the Waikato DHB.
Siddiqui faced 13 charges and his eight-day trial was due to kick off in the Hamilton District Court today, but he changed his plea to guilty on four charges minutes before it was scheduled to start.
The remaining nine charges will be withdrawn at sentencing.
Siddiqui admitted forging two documents - a State of Illinois Department of Financial and Professional Regulation Certificate Licence and an ABPN certificate - between August 12, 2014 and January 22, 2015 to obtain employment at the Waikato DHB; obtaining an NZ Medical Council vocational licence to be hired as a psychiatrist on January 19, 2015; using a title (psychiatrist) to imply that he was a health practitioner between January 19 to July 14, 2015 and obtaining by deception a job at the Waikato DHB on January 19, 2015.
Court documents show he provided three references with his CV. Investigations by police and the FBI proved them to be fake - none of the named referees worked at the hospitals named by Siddiqui, nor had he been employed by them either.
The Waikato DHB was given one oral reference by a Dr Mohan Nataraj. However when double checked it turned out to be the phone number for Siddiqui's brother.
When contacted, Medical Council chief executive Philip Pigou said the ABPN document was critical to Siddiqui getting his job.
The council accepted he was a qualified doctor, but said that after the case, the American Board of Psychiatrists had tightened up its protocol in regards to what information could be obtained from its website. "It seems a bit loose. I know that there has been a review in America," Pigou said. "Effectively what he did was actually obtain a genuine specialist qualification from the American board and then presented that as his own."
Pigou said Siddiqui appeared to notice a loophole on the American board's website that meant he didn't have to fill in a field marked "date of birth" - a key piece of information he didn't have about the real Dr Siddiqui.
An excerpt from the summary of facts shows that had the IMR been more vigilant in its checks, Siddiqui may never have landed in New Zealand.
"On 11 August 2014, the defendant provided IMR with his CV and accompanying documentation.
"IMR did not realise at the time that the defendant had already made approaches to their organisation in 2012 and had been told on those occasions that his work experience and qualifications did not meet the [Medical Council of New Zealand] registration requirements."
IMR has been approached for comment but was yet to respond in time for the Herald's deadline.
The court documents show the medical council did notice a discrepancy between the names of the respective doctors, but that was resolved by Siddiqui who forwarded fake emails.
On January 19, 2015, he was given a job at the Waikato DHB on a salary of $165,250, excluding allowances.
During his five months in the job he also claimed expenses worth $4883.64, excluding relocation costs and flights, whichare still to be confirmed.
The Waikato DHB's director of people and performance, Greg Peploe, said Siddiqui was employed after coming through a "reputable recruiting agency who would have carried out a credential check".
"The Medical Council of New Zealand granted him provisional vocational registration. The DHB employed him verifying his credentials and obtaining the three referee checks.
"All these checks by a number of organisations failed to pick up the issue, which indicates the degree of planning and the complicity of others in the United States in a sophisticated scam."
Siddiqui was convicted by Judge Glen Marshall and remanded in custody for sentencing next month.