Judge Bruce Davidson remanded Keenan until May 24 for sentence, with a pre-sentence report to look at community detention, and a bail condition not to drive.
Police spokesman Grant Ogilvie said only calibrated police breath testing machines could produce readings that were admissible as evidence in court.
"All others give only an indication. They are not an accurate guide to whether you are over the drink-drive limit or not. Anyone drinking to the point where they feel they need to test themselves should be erring on the side of caution and not driving."
Other drink drive convictions:
A Masterton man, 23, was convicted of his fourth drink-driving offence - the third to involve a crash - in Masterton District Court on Thursday.
Nonu Fa'asavala was convicted after pleading guilty to drink-driving with a blood alcohol level of 278mg, more than three times the legal limit of 80mg, on November 19 last year.
Prosecutor Sergeant Greg Peters said Fa'asavala was driving along Cornwall Rd, near Masterton when he lost control of the car, which slid into a power pole and ripped it in half, ripping power lines from nearby houses.
Mr Peters said Fa'asavala had three previous drink-drive convictions, "two of which involved vehicle crashes".
Alec Beaver, 38, of Porirua, was convicted of drink-driving, being a third or subsequent offence, with a level of 754mcg, after attending a concert in Martinborough in February.
Beaver was fined $900 and disqualified from driving for 12 months and one day.
Bianca Groen, 19, of Masterton, was convicted of drink-driving with a breath alcohol level of 483mcg. She was fined $350 and disqualified from driving for six months.
