Mr Alymer, of Ballyvista, Emly, Co Tipperary, worked for the McManus family for 10 years and was earning €459.48 net weekly pay, but was immediately dismissed without pay following the incident on June 9, 2010.
He brought a case against JP McManus's wife, Noreen, trading as Martinstown Stud, and claims that he was unfairly dismissed and did not receive minimum notice.
When dismissed, the security officer was on a written warning following previous incidents.
Martinstown House Manger Colm Hannon said on one occasion Mr Alymer used a blue mesh cloth to cover a CCTV camera which was monitoring the security lodge at the estate's main entrance.
Subsequently, Mr Alymer claimed that security bollards at the estate's main entrance caused €1,500 damage to the underside of his vehicle in February 2010.
Mr Hannon said Mr Alymer raised the bollards and "was trying to extort funds from Martinstown" before he was given a final written warning and suspended for five days.
In the early hours of June 9, 2010, Mr Alymer's supervisor, DJ Roche, along with another man, began a covert operation to see if the estate could be penetrated.
The two men came upon Mr Alymer sound asleep in a security hut at one of Martinstown's three entrances. A security dog was barking loudly at the intruders but Mr Alymer "remained comatosed in sleep".
Solicitor for Mr Alymer, Colin Morrissey, said Mr Alymer was very proud of his position at Martinstown and refuted the allegations made against him.
The tribunal will resume hearing the case next year.