But the jurors deadlocked on monetary damages for Mr. Masson.
A single juror can deadlock the sentencing phase in federal death penalty trials, resulting in a life sentence.
But the jurors deadlocked on how much money to award him.
The same jurors acquitted her son, 31-year-old Raymond Buckey, of 40 charges, but deadlocked on 13 other counts.
The action came five days after the jurors in Mr. Buckey's retrial had deadlocked on all eight charges.
But the jurors deadlocked on another involuntary-manslaughter charge, leading the judge to declare the mistrial.
The jurors also deadlocked on an attempted-murder charge against Mr. Giovanelli.
In the first murder trial, in 1987, jurors deadlocked on each defendant.
Lawyers on both sides said they understood that jurors had deadlocked 11-1 for conviction.
Mr. Ruiz said the vote seesawed over five days, but the jurors finally deadlocked at a firm 10 to 2 to convict yesterday.