Mr Rolfe's solicitor has written to NT police detailing a number of matters of concern.
They included accusations that evidence from an independent expert witness was amended and edited and that evidence favourable to Mr Rolfe was withheld, the NT News reported.
Acting NT Police Deputy Commissioner Michael White confirmed receipt of the letter and that it had been referred to the NT Independent Commission Against Corruption.
"We have received a letter from the lawyer representing Mr Rolfe and we're investigating the contents of that letter and assessing the information that's been provided," he said.
"We'll determine where the investigation goes.
"I'm not going to talk about specifics but again, we'll review the information that's been provided and we'll thoroughly investigate any allegation that's been made.
"I have referred it to the ICAC."
Mr White declined to comment on whether the detective concerned had been spoken to.
In November 2019, Warlpiri man Kumanjayi Walker was fatally shot by Mr Rolfe during a bungled arrest at a house in Yuendumu, northwest of Alice Springs.
Mr Rolfe was charged with the murder of the 19-year-old but was acquitted after a Supreme Court trial.
An inquest into Mr Walker's death is set to resume later this year.
