You'll need to know the rules of evidence for your trial
Get familiar with the rules of evidence. In court, everyone must follow the rules of evidence. These rules say what evidence a judge (or jury) can consider when they make a decision.
For a judge or jury to consider the evidence (what your witness says or anything else you show), you need to follow the rules of evidence. The other side needs to do the same. If they don't, you can ask the judge to not let the evidence in (you can object). You will need to know these rules to make sure that your evidence is considered and to make sure the other side is following the rules.
Basic overview of a few main rules:
- No hearsay: Generally, a witness can't say what someone else said to prove what that person said is true. There are many exceptions to this rule. If you want your witness to be able to repeat what someone else said, make sure you there is an exception to the hearsay rule. Evidence Code section 1200. The hearsay rule applies to documents as well.
- Evidence must be relevant: In general, this means that the evidence tends to prove or disprove something that has to be decided for the case. Evidence Code section 210 and 350.
- No character evidence: In general, you can't present evidence that someone has done something bad in the past to try to show they must be a bad person generally and so probably did what you claim. Evidence Code section 1101
You can find the rules for what evidence can be used in court in the California Evidence Code. A law library should also have other books that help explain the rules. Being able to work with evidence in court is very important for presenting your case or defense. You may want to consult with an attorney to get help with it.