The Vatican has begun its long-promised investigation into the crimes allegedly committed by disgraced ex-Cardinal Theodore McCarrick, with the intent of determining a punishment for the former high-ranking church leader.

McCarrick, who retired as archbishop of Washington in 2006 but remained a globe-trotting diplomat representing the Catholic Church and occasionally the U.S. State Department, was removed from ministry when the church determined in June that he had groped a teenager at a New York church almost 50 years ago.

Then more allegations came to light: The church had twice settled hushed cases brought by men who said McCarrick harassed them when they were seminarians or young priests. A Virginia man, James Grein, said McCarrick abused him for years, starting when he was 11.

In July, McCarrick resigned from the College of Cardinals, retaining the lower title archbishop, and the Vatican promised that he would stand trial in its internal court system. Then, for months, silence.

On Thursday, Grein said that the Vatican's judicial process is now underway. He testified before an investigator representing the church, in an office of the Archdiocese of New York, on Thursday morning.

"I had one of the best days of my entire life today. I changed how people are going to think about the Catholic church today," Grein said to The Post afterward. He expressed confidence that the priest who interviewed him, the Rev. Richard Welch, will share the transcript of his testimony about being abused by McCarrick with church leaders at the highest levels, all the way up to Pope Francis. "Francis knows who I am - he can see me and hear me and listen to my voice and hear my emotions.... It's about time."

Leaders in the Vatican would not provide information on the canonical process which will investigate McCarrick and determine a punishment, if he is found guilty. One punishment the Vatican can hand down is sentencing a person to a life of prayer and penance. Francis already imposed that sentence when McCarrick resigned as a cardinal; McCarrick is currently doing penance in a remote friary in Kansas. More severe options would include defrocking him so he is removed from the priesthood entirely.

The revelation of allegations that such a high-placed leader harassed victims for years, and that many in the church whispered about McCarrick's widely rumored behavior without taking action, sent shock waves through the church. Faithful Catholics were infuriated. McCarrick's case, along with a major grand jury investigation in Pennsylvania that illustrated the extensiveness of sexual abuse by priests there, sparked protests which are still ongoing demanding that bishops resign or seriously rethink their approach to eradicating abuse from the church.

Vatican spokesman Greg Burke said he would not provide information on how the church's judgment on McCarrick is proceeding, and several officials in the New York archdiocese referred questions to the Vatican.

Patrick Noaker, an attorney representing Grein, said that the New York archdiocese's director of public policy Edward Mechmann contacted him last week, asking Grein to come to New York to testify. When Noaker and Grein arrived at the office of the metropolitan tribunal, a branch of the New York archdiocese that more commonly handles marriage applications, judicial vicar Welch showed them an affidavit that he had prepared based on information provided earlier by Noaker.

Welch then informed them, according to Noaker, that McCarrick has been charged with three crimes in Grein's case - one for sexual contact with a minor, one for sexual contact with an adult because the abuse continued past Grein's 18th birthday and another for using the ritual of confession to solicit sex.

"McCarrick would take him into another room and one of the first things they would do is he would hear his confession. Almost every single time," Noaker said. "He would touch his genitals as part of that. He would have to 'confess' both sins of the mind and the body."

Although the vicar interviewed Grein, Mechmann said staff involved in the hearing were not acting in their roles as New York archdiocese personnel, but had instead been "deputized to gather evidence on behalf of the Holy See."

Noaker said that Welch explained he will take the transcript of Grein's testimony and the affidavit to the full tribunal that the Vatican has assembled to hear McCarrick's case. "There at least is some appearance of urgency," Noaker said.

Grein said Welch asked him to recount his abuse. "Part of my PTSD is what happens to me is that I'm now in a room, with McCarrick, as an 11-year-old boy in Teaneck, N.J. It is a horrific experience for me. ... When I come out of that, I cry. I cry like a baby," he said. He agreed to endure the interview because he hopes it will lead to McCarrick being defrocked and the pope publicly apologizing.

At the end, Grein said, Welch said to him, "I need to say sorry."

"I said no. This isn't sorry. This is way beyond sorry," Grein said. "What has transpired today is holy. This is God's work. No man can say sorry to another one after they've been destroyed like I have. It's just not possible. The only way I can get relief is from God."