PHOENIX (AP) - In a bombshell revelation, Sheriff Joe Arpaio acknowledged Thursday that his office was behind a secret investigation into the wife of the judge presiding over a racial-profiling lawsuit against the brash Arizona lawman known for his anti-immigration patrols.

A contempt-of-court hearing in the case took the strange turn after the sheriff finished his testimony and Judge Murray Snow began asking him questions, including whether Arpaio was investigating him and his family.

"Are you aware that I've been investigated by anyone?" the judge asked.

Arpaio said he believed his former lawyer, Tim Casey, had hired a private investigator to investigate Snow's wife after she purportedly made a comment that about the judge not wanting the sheriff to get re-elected in 2012.

"We weren't investigating you," Arpaio told the judge. "We were investigating some comments that came to our attention."

The Maricopa County sheriff gave soft-spoken and terse answers in his second day on the witness stand in the hearing that could lead to fines, increased oversight of his agency and a possible criminal contempt hearing. His answer to several questions was, "I don't recall."

His demeanor lacked the bravado he normally brings to news conferences and TV interviews.

Snow is an appointee of President George W. Bush who has been overseeing the sprawling racial profiling case against Arpaio that's been winding its way through the courts.

The judge determined in 2013 that Arpaio's office systematically racially profiled Latinos during traffic stops and then convened the contempt-of-court hearing this week after Arpaio defied his orders to stop carrying out immigration patrols.

The case has battered Arpaio's legacy. He was once a hero to conservatives across the country for taking on immigration but has seen his political strength weaken with a series of negative court rulings and lawsuits.

His testimony came five years to the day after the signing of Arizona's landmark immigration law known as SB 1070. About 200 protesters marched Thursday to the federal courthouse where Arpaio testified to mark the anniversary and draw attention to immigration policies.

It was not immediately clear what consequences Arpaio could face over the private investigator. Federal law prohibits anyone from trying to attempt to intimidate or inappropriately influence a federal judge.