A man who drugged and raped his 16-year-old sister has been let off with a lenient sentence of 240 days in prison and probation.

The 20-year-old from Crescent City, California, pleaded guilty to giving his sister highly potent marijuana, also known as "dabs," until she could no longer recognise him as her brother.

He said she had repeatedly resisted his sexual advances. The age of consent in California is 18.

Judge William H Follett sentenced him to three years, and then suspended all but 240 days in county jail and probation.

The judge noted the victim took her own clothes off and was not unconscious.

He also questioned whether there was sufficient evidence on which a jury could convict the man, despite him having given a videotaped confession.

Judge Follett said he believed the "stigma" of the rape conviction, along with being listed on the sex offenders' register, was enough of a deterrent to deter the man and others in the community.

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But Del Norte District Attorney Dale P Trigg said he "could not disagree more with" the decision, KRCR reported.

"The message that this sends to our community is that sexual predators who get their juvenile siblings stoned enough can have sex with them without any meaningful consequence," he said.

"That is not the message I want to send to our community.”

He added: “In a lot of ways, this case is more egregious than Brock Turner,” referring to the 21-year-old who served half his six-month sentence for the sexual assault of an unconscious woman at Stanford University.

In the wake of Turner's case, the law was changed to make such crimes ineligible for probation.

Mr Trigg said: “This defendant took advantage of a position of trust as this victim’s big brother. He knew she didn’t want to have sex with him. She told him that repeatedly.

"So he got her stoned on dabs he gave her until she didn’t even recognise him in order get what he wanted.”

Deputy District Attorney Annmarie Padilla also argued for stricter sentencing.

She asked Judge Follett to follow the Probation Department's recommendation of six years in prison, the Crescent City Times reported.

Ms Padilla said: "Under this interpretation of the law, a perpetrator at a college party who chooses to forcibly rape a conscious victim will go to prison.

"However, a different perpetrator at the same party who chooses to watch and wait for a victim to pass out from intoxication before sexually assaulting her may get probation.