This is a tragic story, no question. Setting aside the content, however, I humbly observe that the headline needs to be somewhat carved up.
Whenever you use the word who, there’s a chance you’ve inadvertently spent more words than you need to say what you want to say. (It’s a pronoun, so it’s automatically suspect.) In this example, who restates inmate. The phrase who was just gets you from inmate to stabbed without giving you any additional information.
In this case, CNN.com also switches headline styles — including the article An to go with inmate and a to go with prison yard, but then omitting the article a when they get to lawsuit. Gotta stick with one approach or the other.
A more direct version of the headline might be: Lawsuit says correctional officers left stabbed inmate to die in prison yard.
12 words, instead of 18.
Think how much more you could get done in a day if all the headlines only took you two-thirds as long to read.