The lawyer for a woman accused of murdering her colleague by driving him into a harbour where he drowned, has said that if she had done so deliberately she would be 'committing suicide'.

Giollaiosa Ó Lideadha SC also said that the deceased was probably the one who had pulled the handbrake, but that this was not proof of guilt.

Mr Ó Lideadha  was giving his closing speech to a jury in the Central Criminal Court trial.

Marta Herda, of Pairc Ná Saile, Emoclew Road, Arklow, Co Wicklow, is charged with the murder of 31-year-old Csaba Orsos on 26 March 2013.

The 29-year-old Polish waitress has pleaded not guilty to murdering the Hungarian at South Quay, Arklow.

Both had been in Ms Herda's car when it went into the water that morning. Ms Herda escaped at the harbour but Mr Orsos could not swim and his body was found on a nearby beach later that day.

The trial heard that they had worked together, he was in love with her, but she didn't feel the same way. She told gardaí he had spent two years following her, phoning her and sending her messages.

Mr Ó Lideadha said that the prosecution case was completely unsustainable and did not make any sense. He said there had been a tendency to run with a presumption of guilt.

He said that something amazing had happened in the State's closing speech by Brendan Grehan SC.

"He said to you that some of you might find it fanciful or farfetched that Marta Herda deliberately drove into that water because she had the window open and could swim," he said.

Mr Ó Lideadha said it was a true and important concession.

"I'm happy to allow you to apply your gut here. It just doesn't make sense," he said.

He noted that the prosecution then said that she might have wanted to commit suicide.

"I find this a truly amazing proposition because that's the defence case, that how could she have done this because it would be committing suicide," he said.

He said the evidence contradicted any proposition that she was suicidal.

He noted that the State had asked why Ms Herda had kept a Valentine's card that Mr Orsos had sent if he was harassing her.

"She doesn't concede this but other people seem to see what's going on," he said. "She actually gets something positive out of this as well, someone saying: 'I love you. You're the most amazing person.' Is that a criminal offence now?"

He suggested that this was also the reason she had rung him at 5am on the morning of the incident.

"The suggestion she rang him at 5am to kill him is totally bizarre," he said.

He explained that a murder conviction could be brought in only where there was intent to kill or seriously injure.

"Below that level of intent, there's recklessness: gross criminal negligence involving a high degree of recklessness," he said. "In this case, the driving into the river and the risk of death."

He said that if the jurors decided that she may not have intended it, but was reckless about it and thought about the risk to life, a verdict of manslaughter would be open to them.

"I would submit there's no evidence to support that conclusion," he said, however.

He said dangerous driving causing death was a level below this, but was not on the indictment. He said the prosecution 'decides what goes on and what doesn't'.

He said it would be very unfair, if satisfied murder was out, to convict her of manslaughter because she was driving dangerously, had done wrong and nothing else was available.

He said there were sometimes also civil cases involving negligent driving, and that sometimes accidents just happened.

"We know that sometimes drivers are distracted, maybe a husband and wife arguing," he said. "If an argument becomes so serious that it affects driving, the argument should be stopped or the car should be stopped, but that would not fairly be called manslaughter."

He said he accepted that his client had wanted to maintain positive and friendly relationships with men, even though she didn't want to have a sexual relationship with them.

"Is that a crime now?" he asked.

He said it appeared she wanted a friendly relationship with the deceased.

"Because he was in such an extreme position, she should have just blanked him," he said. "She knows she should have just blanked him and she knows she shouldn't have got into a car with him."

He said that much had been made of the fact that the deceased could not swim and that Ms Herda was a strong swimmer.

He said that she had saved her own life, which was in great peril and, that as soon as she could, she got the message across that there was a man in the water who couldn't swim.

"Why, if this is some cold hearted plan, bother giving this piece of information?" he asked.

He said the issue of her memory loss was both credible and reliable.

"If there was a plan, all she has to say is: 'I remember it well: He interfered with me, I lost control and we went over the edge'," he said.

He referred to a skid mark found at the scene. He noted that this was caused by the handbrake, but said there was also evidence that the pedal brake could have been used.

"What the prosecution is suggesting is that Marta Herda drove deliberately into the water and Csaba Orsos is the one who pulls up the handbrake," he said. "Marta Herda said she didn't see this coming. It could well have been, and presumably was, the case that Csaba Orsos pulled the handbrake. But what's the implication?"

He said that, according to his calculations, it seemed to have been applied less than a third of a second before going into the water.

"This is entirely consistent with the proposition she described: looking at this guy screaming and roaring," he suggested. "He could have pulled up that brake a quarter of a second prior to going over and that's not proof of guilt."

He said it was ludicrous to suggest that his client had driven into the water deliberately.

"Just think of the terror," he said. "It's incredible that she would do it intentionally… or recklessly."

He asked for a verdict of not guilty.

Mr Justice Patrick McCarthy will begin charging the jury of eight men and four women tomorrow morning.