Carrie Underwood became emotional as American Idol contestant Slater Nalley performed a song he wrote for his teacher’s late son Carter, who was killed aged 17.

Expert weighs in on how American Idol's Carrie Underwood has done at winning over viewers

American Idol judge Carrie Underwood broke down in tears and admitted, “I’m not okay,” during an emotional performance by a contestant.

The 41-year-old country artist, who rose to fame after winning the singing competition in 2005, is now returning to the show but as a judge.

In a teaser clip released ahead of the 23rd season of American Idol, Carrie couldn’t contain her emotions as contestant Slater Nalley auditioned with an original song he wrote for his teacher’s late son, who was killed nine years ago.

The video shows the judges discussing how they were in Nashville, Tennessee, for a round of auditions when Mrs Davis, a high school English teacher, walked into the room.

Mrs Davis said she wouldn’t be auditioning, but explained that Slater Nalley, one of her students, wanted to perform a song he wrote about her son Carter Davis, who was killed at the age of 17 in 2016.

Carrie Underwood

Carrie Underwood became emotional during Slater Nalley’s performance and Luke Bryan consoled her 

Slater then arrived in the audition room and was told he had the “coolest introduction ever” thanks to Mrs Davis.

He revealed that while he didn’t know Carter, he felt a presence into his life after learning about him – which is why he felt he “needed to do something” and he wrote a song about him.

The young singer shared the title of the song – Traces of You – and said it was dedicated to Carter.

Performing the song in front of the judges and with his teacher by his side, Slater remembered the late teen’s “crooked smile” and sang emotional lyrics such as, “Your life was like a river running home.”

“One look at you and I just come undone,” Slater sang. “Now you visit me in shadows I can’t reach and I can’t run. In the dark night you always found the sun.

“A moment breaks and you appear. And for a second I swear you’re standing right here. I’d give anything for love to be enough to make it true as the memories come racing into view, these traces of you.”