How to write a witness report
Things You'll Need
Make a list of positive points regarding your subject's character. Stick to generally recognized qualities like honesty and integrity. Then make a second list of qualities that might have an effect on the positives (like not doing something unless he thought he could get away with it or a tendency to minimize white lies). If your second list casts doubt on the first, you probably should not testify---the opposing counsel will draw out these statements in court.
Write your character witness statement in the form of a character reference letter. Address it to the court or "To whom it may concern". Explain how long you've known the subject and in what capacity. Concentrate on experience that may have direct bearing on the issue, particularly if you have known the subject for a long time.
List four or five positive qualities that relate closely to the issue. If the issue is theft or robbery, you may want to emphasize situations in which the subject has exhibited honesty or resisted the temptation to do something wrong. Other situations that are noteworthy are those that require steadiness, concern for others or patience. Leave out your reactions to your subject's actions or situations you have shared---they are not relevant to your friend's current problem. Any personal comment must relate to an aspect of the subject's character.
As briefly and objectively as possible, state
only what you personally know about the subject. Be prepared to back your statement with additional examples. Your character witness statement can help people understand why something occurred. However, avoid drawing conclusions about whether the subject "could have done" what's at issue. That job belongs to the "finder of fact"---the judge or jury.
Be as brief as possible; take no more than one page to make your point. Never use extravagant prose or fancy words. Write your character witness statement as plainly as possible so it will be easily understood. Before printing your statement, ask several people who do not know the subject to read your statement and tell you if it's easy to understand.
Print your statement on a computer or word processor. Check with your subject's attorney or with the court to see if there is a specific form you should use for a character witness statement. Often, an affidavit form is available from the court. If no form is dictated, simply put your statement on paper with a personal letterhead. Rather than putting the date at the top of the statement, date your signature at the bottom by adding a line underneath it. If your statement will be used as an affidavit---a legal statement or testament---it must be witnessed by a third party. The attorney asking for the character witness statement will be able to assist you with this part of the process.Source: ehow.com