It can be extremely helpful to have someone in court with you who knows the facts of your case firsthand and can support your point of view. In many types of cases, such as car accidents or disputes over whether or not a tenant left an apartment clean, witnesses are particularly valuable. However, in other fact situations, witnesses aren't as necessary. For example, if a friend borrowed $500 and didn't pay it back, you don't need a witness to prove that your now ex-friend's signature on the promissory note is genuine, unless you expect the person to claim that it was forged.
A good witness should have firsthand or personal knowledge of the facts in dispute. This means the person saw something that helps establish your case (for example, the car accident, dog bite, or dirty apartment) or is an expert you have consulted about an important aspect of your case (for example, a car mechanic who testifies that your engine wasn't fixed properly). The judge will not be interested in the testimony of a person who is repeating secondhand or generalized information such as "I know Joe is a good, safe driver and would never have done anything reckless," or "I didn't see Joe's apartment before he moved out, but both Joe and his mother, who couldn't be here today, told me that they worked for two days cleaning it up."
Above all, a good witness is believable. This isn't always an easy quality to define. For example, a police officer may be a symbol of integrity to some people, but others will automatically discount much of what he or she says. But remember, it's the judge you are trying to convince, and judges tend to be fairly establishment folk. They make comfortable salaries, own their own homes, and generally tend to like the existing order of things, and most judges would be likely to believe a police officer.
In many types of cases, such as a car accident, you won't have much choice as to witnesses. You will be lucky to have one person who saw what happened. Often this will be a close friend or family member. There is no rule that says you can't have these people testify for you. Indeed, a person's spouse, roommate, or close friend can often give very convincing testimony. But given a choice, it is usually better to have a witness who is neither buddy nor kin. That's because a judge may discount the testimony of people to whom you are close on the theory that they would naturally be biased in your favor.
Try to dispel a judge's cynicism about friends or family who are witnesses. Have a closely related witness bend over backward to treat the other side as fairly as possible. Thus, if your brother is your only witness to the fact that ABC Painting splashed paint on your boat, he might point out to the judge not only that he saw ABC employees screw up, but that it was a very windy day and the painter was understandably having a hard time keeping the paint on the dock where it belonged.
In some types of disputes, such as whether your house was properly painted or the work on the car engine was completed competently, you have an opportunity to plan ahead to locate witnesses. That's because the type of witness you need is usually not an eyewitness who saw the work in progress but instead an expert in the field who can convincingly explain what went wrong. Obviously this type of witness is only valuable if the person really does have good credentials and relevant knowledge so that a judge is likely to believe what he or she says. Thus, in a dispute over whether or not car repairs were properly done, it's preferable to bring a letter from a car mechanic with 20 years' experience who has completed a load of training courses rather than one from your neighbor "who knows a lot about cars."
Here are some things you can do to prepare your witnesses.
As with your own presentation, the best way to be sure your witness really will be able to explain the key facts to the judge succinctly and concisely is to have the person practice his or her testimony in advance. As long as the person sticks to the truth, rehearsing the exact words to say in court is completely legal. I suggest meeting with your witness and a friend you have asked to act as a mock judge. Start by presenting your case to the pretend judge exactly as you plan to do it in court. Then ask your witness to stand and explain his or her version of what happened. Have your friend ask the witness questions about anything that's unclear in the presentation, as a judge would do.
If at first your witness is a little disorganized or unsure, work to develop a coherent presentation that covers all key points. When he or she says something that sounds good, write it down and practice it several times before your court date.