(New York) Singer Ed Sheeran took the witness stand in a New York courtroom on Tuesday to refute allegations that his hit song Thinking Out Loud was copied from Marvin Gaye’s classic Let’s Get It On .

Sheeran was called to testify in the civil lawsuit brought by the heirs of Ed Townsend, who co-wrote the 1973 soul classic with Gaye. The family have accused the English singer of copyright infringement, saying his 2014 track bears “striking resemblances” to Gaye’s famous song.

Sheeran, in a dark suit, was adamant he wrote the song himself. His testimony was controversial at times, as he argued during cross-examination with attorney Keisha Rice.

In response to video footage played in the courtroom that showed the musician moving back and forth on stage between the two songs, Sheeran pointed out that it’s “pretty simple to get songs in and out.” which are in the same key.

“I would be a fool to stand on a stage in front of 20,000 people and do that,” Sheeran said of the accusation that he copied songs.

Earlier in the day, an attorney for the Townsend heirs, Ben Crump, told jurors that merging the two songs amounted to “a confession.”

“We have a smoking gun in front of us,” he said of footage from the concert showing Sheeran switching between the two songs.

Sheeran watched the whole thing while his lawyer, Ilene Farkas, insisted that Sheeran and a co-writer, Amy Wadge, had indeed written the song and that they had not copied the work of Townsend and Gaye.

Sheeran’s chord progression and basic song elements are frequently used and appear in many other songs before Let’s Get It On, the singer’s lawyer pleaded.

The lawsuit was filed in 2017 and the trial is expected to last up to two weeks.