In A Thousand Splendid Suns, why does Mariam refuse to see visitors and have witnesses at her trial?
Mariam does not want to see visitors because she has made her choice to be martyred, or in other words, to take all the blame for her and Laila's husband's death upon her, sparing Laila. If she sees those whom she loves and who are the only people who loved her during her painful life, she is afraid that she will be tempted to tell the truth and that she might not go through with what she feels is her duty.
In regards to witnesses, she cannot have anyone testify because she does not want anyone to know what really happened to Rasheeds, and witnesses might deconstruct her carefully planned story. She is willingly going to her death so that Laila might be spared.