Late today Coroner Smith was alerted that the email was suspect. It had been sent to the family of David Fielding, the 30-year-old flight examiner in a R22 helicopter which collided with a Cessna 152.
The electronic message allegedly came from Professor Frank Sharp, manager of Professional Programmes at Massey University's School of Aviation, who has denied any knowledge of it.
In a statement, the coroner said: "I had no hesitation in calling the police and am keen to get to the bottom of this.
"This is quite an extraordinary development and will no doubt be very upsetting for the families.''
Jan Fielding, mother of David Fielding who was one of the three pilots killed, read the email to the Coroner's Court. It was accompanied by a background resume on Professor Sharp with a Massey University letterhead.
The writer had suggested the family might find the email helpful for the current inquest and said the coroner should have the information brought to his attention.
It covered a controversial topic which has come up throughout the hearing - the "standard overhead join'' which is a manoeuvring procedure for aircraft to join the circuit above some airports in preparation for landing.
There is debate among experts about the safety of the practice and the email gave views on that, along with opinions on what happened at Paraparaumu and in a more recent fatal mid-air collision at Feilding.
"I hope you find this helpful,'' the email ended.
The coroner's office has declined any further comment because the inquest has not yet finished. It has been adjourned until mid-December when experienced Taupo pilot John Funnell is available to expand on overhead joining _ which he opposes.
Mr Funnell supplied a written statement on the first day of the inquest but was not present to be cross-examined.
As well as David Fielding, the student pilot flying the helicopter on February 17, 2008, 19-year-old James Taylor, was killed in the late morning crash above Paraparaumu.
The solo pilot of the Cessna, Bevan Hookway, 17, suffered multiple injuries and died in Wellington Hospital several hours later.