What is the difference between procedural and substantive law?
Substantive law defines the actual law set down by the legislature such as elements of a crime, penalties to be imposed, rules of evidence, etc. Procedural law defines the manner in which the criminal case and its trial will be handled. A violation of a substantial rule of law is more likely to result in a reversal of a conviction. A violation of criminal procedural law is less likely today to result in a reversal unless it relates to a constitutional protection, such as search and seizure, Fifth Amendment, etc. Even here the trend is to limit those areas where a reversal will be possible.