Machado is accused of killing Wallace execution-style in Hughson in November 2016. He was found mentally incompetent a year later.
"Was nerve-wracking," Wallace's wife, Mercedes, told FOX40. "That was nerve-wracking just knowing that the possibility we all know in real life he was competent."
Justice hung in the balance for 15 months. Wallace's family was worried criminal proceedings would stop if Machado was found unfit.
But all of that changed on Monday.
"A little bit of relief, a little bit of pain, but I think finally we get to move forward and get justice for Dennis," Mercedes said.
Machado will go to trial for the murder of Deputy Wallace.
"This helps in the healing process to know that there will be accountability," Wallace's brother, Dave, told FOX40.
And Wallace's family believes he is happy.
"He really truly believed in our justice system," Mercedes said. "He just believed in truth and believed in doing the right thing."
Now, they face an even longer hurdle. They know it could be months -- even years -- before a trial is set and a verdict is reached.
Machado's will be in court on Feb. 13.