A U.S. pastor who officiated at his son’s same-sex marriage faces a church trial Monday.

The Rev. Frank Schaefer, 51, could be defrocked if a jury of fellow Methodist clergy convicts him of breaking his pastoral vows by officiating the 2007 ceremony in Massachusetts. Schaefer’s supporters argue that church teaching on homosexuality is outmoded.

“Public opinion has changed very rapidly,” said the pastor’s son, Tim Schaefer, 29. “I hope this leads to a renewed conversation to revisit these policies to see if they are a little archaic.” He will testify on his father’s behalf.

Frank Schaefer could have avoided a trial if he had agreed to never again perform a same-gender wedding, but he declined because three of his four children are gay.

The nation’s largest mainline Protestant denomination accepts gay and lesbian members, but rejects the practice of homosexuality as “incompatible with Christian teaching.” Clergy who perform same-sex unions risk punishment ranging from a reprimand to suspension to losing their minister’s credentials.

The issue has split the church. Hundreds of Methodist ministers have publicly rejected church doctrine on homosexuality, and some face discipline for presiding over same-gender unions.

Critics say those pastors are ignoring the church’s democratic decision-making process. The denomination’s top legislative body, the 1,000-member General Conference, reaffirmed the church’s 40-year-old policy on gays at its last worldwide meeting in 2012.

Tim Schaefer struggled as a teenager, aware of Methodist doctrine on homosexuality. He said he prayed every night that “God would make me normal, take this away from me.” He contemplated suicide but knew it would devastate his family. Schaefer finally told his parents at age 17, and he said they accepted him completely.

Years later, Schaefer knew he wanted his dad to perform his wedding ceremony.

“I remember thinking I have two choices: I can ask my dad and know I am putting him in a position … where he would risk his career, or I could not ask my dad and really risk hurting his feelings. I think he would have been devastated if I hadn’t asked him,” he said.

Frank Schaefer has said he informed his superiors in the Eastern Pennsylvania Conference that he planned to officiate his son’s wedding, and again after the ceremony. He said he faced no discipline until April — about a month before the church’s six-year statute of limitations was set to expire — when one of his congregants filed a complaint.

A Methodist trial resembles a secular trial in many ways, with counsel representing each side, a judge and jury, opening statements and closing arguments, and testimony and evidence.

Schaefer can appeal a conviction, but neither the church nor the person who brought the charge may appeal an acquittal.