A judge Monday dismissed murder charges against a nurse accused of killing three patients with lethal doses of potassium, saying the prosecutors had done no more than prove she was present when the patients died.

After listening for five weeks to the prosecution's case, Prince George's County Circuit Judge Joseph Casula said that "the state's reach hopelessly exceeded its grasp."

Prosecutors had alleged that Jane Bolding, 30, an intensive care nurse at Prince George's Hospital Center, killed three patients by injecting them with potassium chloride, which can induce heart attacks.

Defense attorneys engaged in extensive cross-examination of the state's witnesses, but did not call any witnesses.

When the prosecution rested its case last week, Bolding's attorney asked Casula to dismiss the charges.

Casula, who has been hearing the case without a jury, recessed the trial Wednesday to study defense arguments that the prosecution's key piece of evidence - a study indicating a high incidence of cardiac arrest during Bolding's shift - failed to prove the nurse was responsible for the deaths.