The court case against AC/DC drummer Phil Rudd comes down to the answer to one question in a Civil Aviation Authority questionnaire he had to fill out when re-applying for his private pilot's licence.

Rudd answered ‘no' to ‘do you use any legal or illegal recreational drugs or substances?' in the medical certification section.

Phil Rudd in Tauranga District Court yesterday.

The CAA says Rudd lied because he was busted in 2010 in possession of 23 grams of cannabis. The Tauranga-based restaurant owner was convicted, and the conviction later overturned on appeal.

Rudd pleaded not guilty to the charge he made a misleading statement in his medical certificate application for a pilot's licence before Judge Louis Bidois in Tauranga District Court yesterday.

Prosecutor Fletcher Pilditch told Judge Bidois there is a ‘mens rea' aspect to the case, which concerns the state of mind of the accused at the time the alleged offence is committed. Did Rudd genuinely believe at the time that his answer was true?

The questionnaire is part of the CAA medical exam, essential for flying. A licensed pilot cannot fly without a current medical certificate.

Rudd's medical certificate was rescinded after the CAA was told about his drugs bust.

Giving evidence in court yesterday, Rudd says the 2010 arrest, the court case, and associated publicity put him off cannabis and he hasn't smoked it since then, and didn't consider it when the question came up during the medical examination with Dr Jeff Brownless.

'In 46 years I have never been busted, I'm not a trouble make or a w*****. By the time I got to see Dr Brownless I would have been clean, probably as long as I have ever been in my whole life, a couple of years,” says Rudd.

'I wouldn't smoke cannabis, or do any recreational drugs apart from smoking and drinking, because I wanted to get my licence back.

'I didn't put anything down there that I knew to be wrong.”

Rudd owned and flew a Hughes 500 helicopter in the early 80s, but sold it and allowed his licence to lapse while he raised a family.

"You can have kids or a helicopter - you know how it goes,” says Rudd.

He bought another helicopter in 2011 after doing three tours with the band AC/DC.

'I was back on the road for three tours, worked harder than a Bering Sea fisherman, and I made a lot of money and thought I would buy a helicopter. I've got everything else. Have you seen my garage?”

Rudd says he was lucky to be able to purchase the MD520N as only 13 were available to civilians, all the rest were military.

Because he hadn't flown for more than 20 years, and CAA licencing had changed, and Dr Brownless said he had to treat Rudd's application on June 13, 2012 as a new one.

Cross examination of Dr Brownless by Rudd's barrister Paul Mabey QC revealed issues with the wording of the CAA questionnaire, and conflict over who filled out various parts of the form.

Rudd says the doctor filled out most of question 20, which includes the use of drugs, with other medical questions, like have you experienced a pulmonary embolism and deep vein thrombosis.

Rudd says he recognises the deep vein thrombosis question because he's a pilot. He doesn't know what a pulmonary embolism is, and maintains the doctor ticked them off as he gave his answers.

In cross examination Dr Brownless denied filling out the form for Rudd, pointing out differences in the way the answers are given, he ticks them, and says Phil circles them.

His log book was also called for, but Rudd didn't have one, and pleaded guilty to an amended charge of failing to maintain a logbook between August and April 2012.

Judge Louis reserved his decision until 4pm today.