Scene 2 is played at a fever pitch. What does it imply about Macbeth and Lady Macbeth as far as Duncan's murder is concerned?

Both L. Macbeth and Macbeth are pretty shaken over the murder of Duncan. One might even see them as the most inept murderers in Scotland. They are clearly not cut out for this. Macbeth forgets to mark the guards with blood. They are both standing around with blood dripping from their hands in a shocked state. They muse about what they have done instead of cleaning up. L.Macbeth even has time to call her husband a coward.