As previously stated in the comments, the combination of morphine and ativan is a poor choice to induce death:
Morphine and Ativan, one of the drug combinations that a Foti witness says were administered to the patients, is an extremely unreliable way to induce death, pharmacologists and forensic pathologists say. It is used to relax agitated patients and to relieve severe pain.
The experts contacted for this story differed in their views on the other drug combination mentioned in Foti’s report: morphine and Versed. But the consensus view is that Versed, while commonly used as a palliative and relaxer during surgery, is an equally poor choice if the goal is to induce death.