The father of former Casper Dr. Shakeel Kahn has no right to the cash or other property federal agents seized from his son during their investigation of his prescription drug-dealing crimes, according to the Wyoming U.S. Attorney's Office.

Rahim Khan, a Canadian citizen, filed a petition in U.S. District Court saying Shakeel was holding $675,000 in cash for safekeeping or had used it to buy residences and vehicles.

But Wyoming Assistant U.S. Attorney Stephanie Hambrick responded that Rahim Khan had little to no evidence for that. "R. Khan cannot show that any money of his was used to purchase the vehicles and houses, all he has is speculation."

The petition and response mark the latest twist in the five-and-a-half-year-old case that went public three years ago with the arrests and later charges against Shakeel Kahn, his wife Lyn, his brother Nabeel, and two other defendants.

In May, a jury convicted Shakeel Kahn on 21 counts including prescribing medicine resulting in death, operating a continuing criminal enterprise and possessing a firearm during a federal drug-trafficking crime. He received a 25-year prison sentence.

Shak Kahn via Facebook

Nabeel Kahn was convicted and sentenced to 15 years one month for conspiracy to distribute oxycodone and other drugs, and for possessing a firearm during a federal drug-trafficking crime.

They have appealed their cases to the Denver-based 10th U.S. Circuit Court of Appeals.

During the investigation, law enforcement agencies seized one house in Casper and two in Fort Mohave County, Ariz.; $1,048,000 in cash in one of the houses in Arizona; more than $100,000 from bank accounts; vehicles; weapons and other property. Of the cash, $580,000 was returned the Kahns.

Prosecutors filed a notice of forfeiture on July 12. People who believed they had a claim to any of that property had 30 days after Aug. 10 to file a claim for it, according to court records.

On Sept. 3,  Rahim Khan, filed a petition saying Shakeel was lawfully keeping $675,000 of his own cash and used some of it to buy vehicles and houses. "It would be unjust for any of the defendants and/or the federal government to be enriched in the amount of $675,000 in combined currency and real property that belongs to Petitioner Rahim Khan, an innocent bystander who was barred from asserting his third-party rights until now."

Hambrick responded that Rahim Khan has a few problems with that assertion.

He hasn't shown how he has a legal right, title or interest in the forfeited property because his name isn't listed in any public records about the purchased properties or vehicles in Arizona, Hambrick wrote.

Saying that he has an interest in the properties isn't good enough, and he would have to prove his money was with Shakeel kahn before the drug crimes, she added.

Rahim Khan probably has a bigger problem than that, because he said he and his wife brought $675,000 in cash from Canada into the United States, and he has no proof of that, either, Hambrick wrote.

If he did bring in $675,000 into the U.S., the U.S. Department of Homeland Security has no record, she wrote.

People who bring in more than $10,000 must declare it, Hambrick wrote. "Failure to file this report is bulk cash smuggling, a felony offense...."