Complex sentence: Since 1949, the most common method has been execution by firing squad, which has been largely superseded by lethal injection, using the same three-drug cocktail pioneered by the United States, introduced in 1996.
Split into simpler sentences: Since 1949, the most common method of execution has been execution by firing squad. This method has been largely superseded by lethal injection, using the same three-drug cocktail pioneered by the United States, introduced in 1996.