Glossary
Burden of proof
The obligation to convince the court of a particular fact or claim. In civil cases, the plaintiff usually bears the burden. The level of proof required depends on the kind of case.
If you have the burden of proof and you fail to meet it, you lose: even if no one disproves your claim. "I don't have enough evidence to decide" goes against the side with the burden.
In civil cases, the burden is normally on the plaintiff for their claims, and on the defendant for any affirmative defenses they raise. In criminal cases, the burden is always on the government to prove guilt; the defendant doesn't have to prove innocence.
The amount of proof required varies. Most civil cases use "preponderance of the evidence" (more likely than not). Some civil matters (fraud, certain family law issues) require "clear and convincing evidence." Criminal cases require proof "beyond a reasonable doubt": the highest standard.