Can a person die if they have had severe constipation?

Rare but yes... Severe constipation can rarely cause hard, dry stool to erode through the colon wall. Peritonitis can occur, and death is a possibility. Having said that, most people's constipation will never become that extreme. Drink lots of water and increase your fiber intake- psyllium is a good fiber supplement. And see your doctor for help!
Rarely. As the primary cause of death, probably uncommon. However, blockage of the colon can lead to many severe chemical abnormalities in the body, the potential for severe nutritional impairment etc. Severe constipation mainly results in great lowering of the quality of one's life. A gastroenterologist is a good person to see, although many pcp's treat this daily.