Evidence that has been collected unlawfully
The Irish Constitution guarantees the people of Ireland certain fundamental rights. Sometimes, the Gardaí or the prosecution in a case can get evidence for a trial in breach of your fundamental rights. This means that they got the evidence in circumstances where your constitutional rights have not been respected.
Evidence collected in breach of your constitutional rights
Evidence that is collected in a "deliberate and conscious" breach of your constitutional rights cannot be presented in court, except in exceptional circumstances. "Deliberate and conscious" means that the Gardaí or officers involved knew that the evidence was collected in breach of your constitutional rights.
For example, if Gardaí found evidence when searching your home, knowing they didn’t have a valid search warrant, they would have collected this evidence in breach of your constitutional rights.
However, evidence obtained inadvertently in breach of your constitutional rights may be allowed in court. However, the prosecution must prove that mistake made was inadvertent.
For example, if Gardaí found evidence when searching your home, not knowing that there was a minor defect in the search warrant, then this evidence may possibly be allowed.
Evidence collected in breach of non-constitutional law
In some situations, evidence may be obtained in breach of legislation or other laws but not in breach of the Constitution. This category of evidence is often called illegally-obtained evidence.
For example, the Constitution does not give the same protection to a business premises as it does to a home. Nonetheless, the power to search such premises often has be given by legislation and any search must be conducted in accordance with that legislation.
If a search is conducted on a business premises not in accordance with the relevant legislation, any evidence gathered is not automatically inadmissible in court. It is up to the judge to decide whether to allow the evidence after considering all the surrounding circumstances.
You should get legal advice for more detailed information on this.