There are many reasons you might miss a period. Simple things such as stress or exercising too much can cause a missed period and many girls are irregular during the first few years of menstruating. But if you've missed a few periods, be sure to see your healthcare provider.
Courts usually find probable cause when there is a reasonable basis for believing that a crime may have been committed (for an arrest) or when evidence of the crime is present in the place to be searched (for a search).
Probable cause requires stronger evidence than reasonable suspicion. In order to obtain a search or arrest warrant, a law enforcement agent must prove probable cause to a judge or magistrate. If a search or arrest is made without a warrant, the officer must prove that there was probable cause. Any evidence obtained without probable cause may be suppressed in court. There are four categories into which evidence may fall in establishing probable cause. Observational evidence is based on what the officer sees, smells, or hears. If an officer observes a suspicious person looking into car windows and carrying a baseball bat late at night, it would fall into this category.