I remember being impressed by the 1998 thriller Jagged Edge when I first watched it. The plot (in case you don't remember) involves a prominent Editor (Jeff Bridges) accused of killing his wife brutally. He hires a lawyer to defend him (Glenn Close) who falls in love with him, blurring her clarity about his guilt or innocence (hence providing much of the tension in the plot).
Early in the movie the audience sees the murder being committed, but the murderer hides their identity. As a police expert pointed out to me later there is no reason (in the movie) why the murderer needs to conceal their identity other than to deceive the audience until the reveal at the end. They kill any possible witness to the crime so there is no reason to hide their face.
Am I wrong or is there some internal logic to the concealment?