Short answer. No. Evidence of the good character of a witness is not admissible until that character has been impeached. You cannot bolster a witness in advance. Support of this kind becomes available only after the other side has attacked the witness's character, and it applies in criminal and civil cases alike.
What the law says
Evidence of the good character of a witness is not admissible until such character has been impeached.
Rule 130, Section 54 — Character evidence not generally admissible; exceptions. Read the full provision →
What the law says
proof may be made by testimony as to reputation or by testimony in the form of an opinion
Rule 130, Section 54 — Character evidence not generally admissible; exceptions. Read the full provision →
The rule is one of sequence
Section 54 of Rule 130 provides that evidence of the good character of a witness is not admissible until such character has been impeached. The prohibition is about timing rather than about the value of the evidence. A party may not build up a witness's character as part of presenting him, because at that point nothing has been said against it and the evidence answers a question no one has raised. Once the character has been impeached, the position changes and supporting evidence becomes available to meet the attack.
It applies in criminal and civil cases
The clause on witnesses is grouped under a heading covering both criminal and civil cases, which sets it apart from the two clauses before it. Those earlier clauses deal with the character of the offended party and of the accused in criminal cases, and with the moral character of a party in civil cases, and each carries its own conditions. The witness rule cuts across both. Whatever the nature of the proceeding, a witness's good character waits until it has been put in issue by the other side.
The general bar this sits inside
Section 54 opens with the wider principle: evidence of a person's character or a trait of character is not admissible for the purpose of proving action in conformity with it on a particular occasion. The concern is that character evidence invites a court to reason from what a person is generally like to what he did on the day in question. The exceptions that follow are limited and each is tied to a defined situation, which is why they are read as exceptions rather than as an open invitation to explore anyone's reputation.
How character is proved when it is allowed
Where character evidence is admissible, the section also states the form it may take. Proof may be made by testimony as to reputation or by testimony in the form of an opinion. On cross-examination, inquiry is allowable into relevant specific instances of conduct. And where character or a trait of character is itself an essential element of a charge, claim or defence, proof may also be made of specific instances of conduct. So specific incidents are available in defined circumstances rather than as the ordinary way of establishing character.