After legal wrangling by his lawyer, John Billington, QC, the charge was amended to one of acting as her lawyer "while in an intimate personal relationship" with her.
The amendment meant the case was adjourned to give counsel time to make further submissions.
The tribunal was told that in June 2010, Mr Horsley met the woman at a Rotorua motel where they had sex for the first time. She was 18.
The next day, while she was driving to Tokoroa, she was involved in an accident and was charged with careless driving and driving with excess breath alcohol. She contacted Mr Horsley from the police station and he went to pick her up.
Mr Horsley told the tribunal he did this "both as a friend and as a lawyer" but said there was "no guarantee" he would end up representing her.
He had represented her earlier when she appeared before the Youth Court in 2008 and 2009, and he said he had viewed her as a "former client" and had not spoken to her for some time when she texted him to meet up for a coffee "out of the blue".
Things came to a head in August 2010 when she spotted him in the Tauranga court one morning. The tribunal was told she rushed at him with "expletive-laden abuse" and, in front of a busy court foyer, announced that she was pregnant and the baby was his.