The sentencing trial of Zacarias Moussaoui teetered on the brink of a mistrial today, as the judge in the case angrily said she might spare him the death penalty following the disclosure that a government lawyer had improperly coached some witnesses.

She also scheduled a hearing for Tuesday to look into the improper sharing of information with seven witnesses — some of whom were scheduled to testify for the prosecution and some for the defense. The lawyer involved in the incident was identified by a federal official as Carla J. Martin of the Transportation Security Administration.