Criminal Evidence
General
The criminal process is adversarial. Each side puts forward its evidence. Evidence is anything which tends to prove the relevant facts in issue. The evidence is directed towards proving the key facts. The key facts are set out in the summons or indictment. These are the facts that constitute the alleged offence.
Evidence is offered by the prosecution which tends to show the truth or otherwise of the matter that is an issue. Evidence can be direct evidence of the facts or can be other evidence which tends to prove the facts concerned as a matter of logic.
Most persons are both competent; able to give evidence and compellable; they  must if required give evidence.  A person can be required to appear and give evidence. That person must truthfully give evidence and answer all questions put.In most circumstances, a spouse will not be compellable as a witness.
Certain evidence which may be logically relevant is excluded for various reasons. In criminal cases some evidence is excluded because it was illegally obtained. Other evidence is excluded because it is presumed to be unreliable.
Hearsay evidence is evidence of statements made outside court offered as evidence of their truth. The objection in principle, is that that the party against whom the evidence is offered, does not have the opportunity to cross-examine the maker of the statements, so as to tend to cast doubt on it.
Certain notorious facts or matters of public knowledge do not need to be proved. The law itself is deemed known to the court and does not need to be proved.
Burden of Proof
In a criminal matter the state has the burden of  proving all relevant facts beyond a reasonable doubt. In contrast, in civil cases, the claimant need  only do so on the balance of probabilities. If  after the end of the prosecution’s evidence, there is not sufficient evidence on each material fact, even if unchallenged, the defendant is entitled to apply to the judge for an acquittal.
Where the defendant has to prove certain facts, which give rise to reasonable doubt as to  his guilt, it is enough that he  establishes such facts on the balance of probabilities. i.e. the evidence shows that the facts are more likely that not to be the case.
In the same way, if a person is relying on an exception or a defence this must generally be proved on the  balance of probabilities. In the case of some regulatory offences, the particular legislation may put the onus of proof in relation to some issues on the accused.
It is a fundamental principle of the presumption of innocence, that the person accused need not  give evidence against themselves. A person is generally entitled to remain silent and need not give any explanation for his  conduct. A jury or judge finding facts must not draw any adverse conclusion from their failure to give evidence.
Corroboration
In criminal cases certain types of evidence are subject to particular controls and requirements for corroboration. Corroboration means further proof over and above the particular type of evidence offered.
This is because the type of evidence is presumed to be potentially suspect or weak. In the case of a jury trial, it must be warned of the danger  of convicting without corroboration. In other cases, corroboration is required as a matter of law.
Corroboration may be required for  certain classes of evidence including evidence of accomplices , confession evidence, evidence as to identification  circumstances.
The requirement is designed to avoid the risk of false confessions or mistakes as to identification. Certain warnings must be given.
Character
Evidence of a person’s bad character is generally not admissible. The policy is that its prejudicial effect might outweigh its probative value; its use as evidence. Generally,  evidence may not usually be given as to a person’s general tendency or disposition to act in a particular way. Similarly, evidence of bad character may not generally be offered as evidence of having committed a particular offence.
Evidence of conduct on other occasions which is of no particular relevance to the occasion concerned is generally inadmissible. , there are certain circumstances where it is specifically permitted.  If the evidence shows a system rebuts  a defence or shows a particular marked and clear tendency, it may be admissible.
Evidence may be offered of a person’s character,  if he puts his character in issue or if he  challenges the credibility of the prosecution’s witnesses. This would involve impugning the credibility of prosecution’s witnesses, over and above simply challenging their evidence in the way necessary for the defence. For this reason, evidence of previous convictions is generally not allowed.
Investigatory Powers
Illegally obtained evidence may be excluded. Where it is obtained as a deliberate and conscious violation of the accused’s Constitutional rights, it must be excluded in the absence of extraordinary excusing circumstances.
There are numerous statutory powers – for investigating authorities such as the Gardai to search for and take evidence. The terms of the power must be strictly complied with because they are limitations on the general liberty of citizens. The law in this area is very bound up with Constitutional rights and human law rights.
Generally, in order to arrest a person, there must be reasonable suspicion that he or she has committed a specific offence. The Supreme Court has held that there is an implied right to arrest at common law. There is a statutory right to arrest for offences carrying a sanction of imprisonment for five years or more
Arrested persons may be generally be searched. Evidence taken may be used in support of a charge. A search warrant is usually required in order to search a building. It is nearly always required to search a dwelling house. The conditions of the warrant must be strictly complied with. Applications for the warrant are made in a summary manner to the District Court judge.
Opinion & Hearsay
Opinion evidence cannot generally be given. A person can generally  give evidence only on matters which he has observed. He should not  draw inferences from those facts. This is a matter for the court or jury. Experts in the areas they give evidence in those areas provided their expertise is first proved.
Hearsay evidence is evidence of a statement other than one offered as truth of its contents, which has been made outside court. It may be spoken or implied. The exclusionary rule does not apply where  the truth or otherwise the statement is immaterial.
Sometimes words spoken by persons outside court, will be relevant to an issue regardless of their truth. For example, if a criminal threat is made the truth of the words would not generally be relevant. Words may also be relevant to show person’s state of mind or having knowledge of a particular matter. They may show evidence of state of mind or emotion.
Confession
An admission against interest is admissible even if made outside court. This is because it is presumed that a person would not ordinarily  make a statement contrary to his interests. The fact of making up such a statement can be offered as proof. In the criminal context an admission may be a confession.
A confession must be excluded unless the court is satisfied that it was made voluntarily, without any inducement or threat.
The courts are aware of the risk of false confessions particularly under police pressure. For this reason, the confession must be proved to have been voluntarily given. It must not be obtained by reason of fear of prejudice or hope or advantage held out by a person in authority. The prosecution must prove that the confession is voluntary.
The so-called Judges Rules require that in criminal cases a person should be given a caution before answering questions. Evidence may be (but need not necessarily) excluded by the judge, if it is obtained in breach of the judge’s rules.
Other exceptions to hearsay include spontaneous statements or acts including those accompanying an event. Spontaneous statements made in connection with a relevant issue may be admissible. They may be evidence of state of mind and well as contemporaneous circumstances and physical conditions.
Documents
Legislation permits certain documents to be admitted as evidence  in criminal trials even though they might otherwise be in breach of the hearsay rule This includes documents which are compiled in the form of records where records, where they  are compiled in the course of a business by person who may  reasonably be supposed to have knowledge of the matters concerned.   This is relevant to records which are compiled in the ordinary course of business. Prior notice must be given of the intent to use this evidence.
The court may nonetheless exclude documentary evidence in the interests of justice, even where it would be permissible under the legislation. The court must have regard to whether the information is reliable, authentic, or would operate unfairly to the accused.
Copies of documents may be put in evidence irrespective of whether the original is available. They must be authenticated in a manner approved by the court. Documents include film sound recordings, audio visual recordings, et cetera,
The Criminal Justice 2006 Act exact allows statements to be admitted which are previously made by persons who refuse to give evidence on oath. It also  widens the circumstance in which a certificate as evidence of certain matter.
Examination
Examination-in-chief also called direct evidence is that elicited by the party tendering the witness. Generally leading questions may not be asked. However, leadings questions are permissible by express or implied agreement, for example  in relation to undisputed facts which are necessary to establish the background.
Cross-examination is undertaken by the other  party’s representative. Cross-examination seeks to cast doubt and challenge the witness’ version of events or to challenge credibility, recollection, et cetera. The party who tendered the witness may re-examine the witness, but only to clarify matters raised on cross-examination. New evidence may not be sought.A question must be asked in good faith to elicit an admissible relevant and material fact.
An objection can be made to a leading question on the basis that it is leading or seeks a response which is inadmissible or  irrelevant.   For example, an attempt to introduce hearsay or other evidence that is not admissible, may be the subject of an objection. to.
Conclusion
A plea is usually  made by the party’s representative to minimize sentence. This is often referred to as a plea in mitigation. In the plea in mitigation circumstances such as lack of previous convictions, cooperation, apology, offer of compensation, prospect of alternative employment, family circumstances may be offered.
There may be an adjournment of the case for the purpose of ascertaining suitability of supervision by for a probation officer or to determine whether a fine, compensation or imprisonment are appropriate.