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).
What does indirect causation mean? A direct cause is when you can determine beforehand the result: for example a car accident makes a dent on the car, or injures the passengers. An indirect cause is a chain of effects, that are difficult or impossible to predict.