Three significant literary techniques Stevenson uses to reveal Markheim's character traits in "Markheim" are the use of reflection, reminiscence of past activities and his doppelganger. In the first, the presence of the hand mirror gives Markheim an opportunity for a literal and metaphorical good hard look at himself. In fact, while holding the mirror, he calls it a "hand conscience" thus indicating that he is precisely thinking of how he could possibly be acting the way he is acting and having the intentions that he has. (This has some similarities to Dostoyevsky's Crime and Punishment when Raskolnikov is at Alyona's apartment.) This reveals Markheim's sense of conscience, sense of right and wrong and true moral guilt, even though he protests to himself that he feels no guilt over his choice and act.
In a literary technique of flashback, Markheim later reminisces about his earlier days when he had religious beliefs and was engaged in religious activities; it was also a time during which he was a more moral person. This shows Markheim's foundational character traits, the traits that were with him in the beginning but have been trampled upon by hardships and desperation.
The third literary technique Stevenson uses to reveal Markheim's character traits is the doppelganger, which is a German word meaning "double-walker." It is said to be an alternate but identical presence of someone, a projection of a person's energy field. Markheim's doppelganger comes walking up the stairs and encourages him to put aside his false conviction that since he is in desperate straits, God will understand and forgive his reason for murder; encourages him to face the truth about his evil side, to see how far he has actually fallen.
The doppelganger reveals Markheim's character traits of self-delusion and pride that make him think murder is all right for him because he has special circumstances. It also reveals that Markheim still possesses the values, morals and beliefs of his past when these reawaken and he is led to truthfully and humbly confess and face his execution.