A garda has gone on trial today accused of carrying out a campaign of harassment against the ex-wife of her partner.

Eve Doherty denies harassing Elizabeth Howlin, who worked in the office of the Director of Public Prosecutions (DPP) at the time, over an 18-month period.

This morning, a jury was sworn in at Dublin Circuit Criminal Court for the trial which is scheduled to last three weeks.

Ms Doherty (aged 49), a Dublin-based garda, has pleaded not guilty to harassment of Ms Howlin at locations in the State on dates between September 21, 2011 and March 16, 2013.

Opening the case, prosecutor Kerida Naidoo SC told the jury that it is alleged that Ms Doherty carried out a campaign of harassment against Ms Howlin.

The campaign allegedly included sending insulting and abusive communications to Ms Howlin's mobile phone, sending an abusive letter to her place of work and distributing abusive leaflets.

Mr Naidoo said that the material included allegations that Ms Howlin prevented a neighbour from being prosecuted for a drugs-related offence.

As a result of this material, Ms Doherty is also charged with two counts of knowingly making a false statement claiming Ms Howlin attempted to pervert the course of justice.

It is alleged that on March 1, 2012 at Carysford Estate, Blackrock, she made this false statement in a leaflet and that on March 31, 2012 she made this false statement in an email. She has also pleaded not guilty to these charges.

Mr Naidoo said that at the time, the defendant was in a relationship with the ex-husband of Ms Howlin. He said that the alleged harassment was carried out anonymously.

He said that the charge of harassment must involve someone, without lawful authority or reasonable excuse, persistently following, watching, pestering, besetting or communicating with another.

He said these actions must be shown to seriously interfere with the other's peace and privacy or causes alarm, distress or harm to the other.

He told the jury it must decide if what happened was harassment. He said it must then decide if the actions were done by the accused and he said this was the big issue in this case.

Mr Naidoo said the accused is entitled to the presumption of innocence and that just because somebody is charged with a crime it doesn't mean they are guilty.

He said that in some cases motive was important but in other cases the motive of a person could be irrational.

He said that in such cases looking for a logical motive might be like searching in the dark.

The trial continues before Judge Melanie Greally and a jury.