Alibi

In a criminal case, once the prosecutor has a defendant an essential element of his case is proving that the defendant was present at the scene of the crime at the time the crime was committed. If the defendant raises an alibi, he is denying the claim of the prosecution that he was present and by implication, if not expressly, that he is guilty.

The defendant need not address the details of the crime at that point; once he produces evidence supporting his alibi it is incumbent on the prosecutor to prove the defendant's presence beyond a reasonable doubt. The defendant need only raise reasonable doubt as to his presence at the scene; this may not require even the preponderance of evidence on the issue.

An acquittal is required if the jury is left with reasonable doubt upon consideration of all the evidence presented by both sides in the case. The alibi's establishment of reasonable doubt regarding presence is alone not sufficient for an acquittal; it may only contribute to reasonable doubt regarding the charge in its totality.

Evidence of an alibi is not excluded if the defendant is unable to account for every minute of the time period in question. Inadequate evidence on the alibi is simply included with all the other evidence a jury must consider in order to determine if there might be a "net" determination of reasonable doubt.

The alibi defense is not allowed in a conspiracy case. Since there is more than one individual involved, the presence or absence of a defendant at the place and time of a crime is immaterial. An alibi would be relevant, however, with regard to presence (or absence) at the scene of the conspiracy's formation.

Legitimacy

Generally, an alibi is a legitimate defense. An instruction from the bench need be given only if requested and only if there is sufficient evidence to validate the defense. Some courts feel that the alibi is covered by general instructions covering reasonable doubt, burden of proof, etc.

Some courts will give cautionary jury instructions, warning that it is a defense that calls for careful scrutiny. But courts have also been found in error for disparaging an alibi. An instruction may be required where the alibi is the defendant's main defense, where the body of evidence is circumstantial, or where the crime is serious and the punishment severe.

In many jurisdictions, the defendant is required by statute or rule to disclose the details of his alibi to the prosecutor. Failure to do so will result in exclusion of the alibi. The validity of this requirement has been upheld by the Supreme Court, cautioning in its opinion that eleventh hour defenses such as last minute alibis are unacceptable in the adversary environment of a trial.

In a subsequent case with turnabout circumstances, the court ruled that the absence of a reciprocal rule requiring the prosecution to advise the defense of its witnesses scheduled to testify in rebuttal of the alibi was also unacceptable. The court held that "discovery must be a two-way street."