Mock Trial and I'm the defense lawyer. What questions to ask?

A man is charged with the murder of his wife. She was found face-down in her bathtub. She died later that day in the hospital. The cause of death may have been cardiac arrest due to either natural causes, suicide, accident or due to a criminal agency. The ppl to question are a drowning expert, pathologist, doctor at the hospital emergency ward, neuropathologist among others. What should i ask or find out?