Lack of evidence can essentially put an end to a person's legal case. Evidence refers to information that the plaintiff, prosecutor or defendant presents to the court to get the court to rule in his favor. Evidence can take many forms, such as witness testimony, DNA or forensic evidence, or anything else that helps the judge or jury determine that one or the other party has proven the elements of his case. If one party does not have evidence to back up the things he is saying to the court, then the court or jury must not side in his favor.
Lack of evidence can happen for a number of reasons. Sometimes, a party may have evidence but it may be inadmissible due to various rules of evidence. For example, if the police illegally searched someone's home without a warrant, any evidence discovered in the search of the home would be barred from being presented to or considered by the judge or jury in the case. In addition, under the rule called "fruit of the poison tree," any evidence that law enforcement officials collected as a result of information obtained from an illegal confession or search would also be inadmissible. This can result in a lack of evidence.
A party to a case may also experience a lack of evidence if he simply cannot find the proof of the case he is trying to make. For example, a prosecutor may be unable to find sufficient witnesses or hard evidence to link a defendant to a crime. A plaintiff may be unable to find the document that proves the defendant committed fraud.
The person who does not have evidence cannot win his case. Each party to a case has a specific burden. For example, in a criminal case, the prosecutor has the burden of proving beyond a reasonable doubt that the defendant committed the crime. The defendant, on the other hand, has the burden of either proving an affirmative defense or introducing a reasonable doubt. These burdens must be met for a party to prevail or win his case; and the manner in which these things are proven all require some type of evidence.
If a lack of evidence exists, a motion to dismiss may be appropriate. This occurs when the opposing party points out the lack of evidence and asks the court to please end the case since the other side can't possibly prove what it is trying to prove. A motion for a summary judgment may also be appropriate when there is no evidence to prove one or more elements of a case; such a motion is a request to the court that it end a trial early since there is no possible way the other side can win since it hasn't proven that the law entitles it to anything.