She felt it was her duty, either to see the completion of justice or to acknowledge the price of failure; someone's life, someone's husband or father, someone's son. Whenever Meera or Liane questioned her late nights, admonished her for overwork, Alethea remembered that Westeros justice could be cruel and absolutely final.
If she had not asked the right questions, if she had not looked down every possible avenue, an innocent man or woman could also die and that miscarriage of justice compounded the tragedy of the original crime.
So she watched, bitterly, angry at herself, and did not flinch.