A man who mailed a source of contraband narcotics embedded in ink into Minnesota state correctional facilities last year will now spend two decades in federal prison for charges that stemmed from a state Corrections Department probe.

U.S. District Judge Wilhelmina Wright imposed a 20-year federal sentence on Walter Davis, 40, of St. Paul, Friday on charges including distribution of a drug analogue, possession with intent to distribute fentanyl and illegally possessing firearms as a felon. Wright's sentence was five months more than what prosecutors had sought in the case.

Assistant U.S. Attorney Ruth Shnider, in court filings before last week's sentencing, described Davis as representing the "true lifeblood of prison contraband schemes." She warned about a rising scourge of drug-soaked letters entering prisons around the country – causing multiple facilities, including those in Minnesota, to suspend delivery of prison mail altogether.

Davis, also known as "Disney," pleaded guilty to the charges three days into a June bench trial before Wright.

According to court documents, investigators singled out Davis as the likely source of drugs concealed in letters sent to inmates at state prisons in March 2021. The investigation started when Stillwater correctional staff noticed two pieces of mail with suspicious markings, and the Minnesota National Guard detected methamphetamine in the envelopes using an ion scanner device.

The next month, investigators intercepted six letters that Davis tried to send to inmates in Stillwater, Oak Park Heights, Faribault and Rush City prisons. Those letters contained news articles printed on Strathmore cotton paper and were found to be soaked in a synthetic cannabinoid substance. The substance, MDMB-4en-PINACA, produces hallucinogenic effects when consumed.

Prosecutors said that the letters Davis sent to inmates were intended to be torn up and sold behind prison walls. The drugs could be ingested either by smoking or eating the paper.

The U.S. Postal Inspection Service helped the state corrections department with the case. Upon seizing the six letters, investigators searched two residences Davis frequented in Maplewood and Eagan.

According to court documents, they found a loaded revolver at each location, a pound of fentanyl at his Maplewood apartment, digital scales, thousands of dollars in cash, a spray bottle containing the synthetic cannabinoid, Strathmore cotton paper and a blender prosecutors said Davis used to mix fentanyl into heroin.

Davis, himself a former Minnesota prison inmate, has multiple convictions dating to 2005, including property damage, theft, aggravated robbery, burglary and theft of motor fuel.

Beau McGraw, Davis's defense attorney, argued for a lesser sentence of 10 years. McGraw argued that Davis' crimes occurred "over a very short period of time" and that "it is important to recognize that no one was injured" because of Davis' actions.

In seeking leniency, McGraw painted a harrowing picture of Davis' upbringing, which was rife with gang violence in St. Paul. Davis has been shot 18 times, most recently once last year. McGraw wrote that Davis was at one point a member of the Rolling 90s Crips gang, but that he ended his involvement in 2012. Shnider argued that it was implausible that Davis had no affiliation with gang activity for the past decade.

McGraw argued that Davis "committed the crimes solely for financial benefit and to have money for him and his family."

"Mr. Davis believes in helping his family financially where he can. Mr. Davis was motivated to commit the crimes to receive money to help his family."

Assistant Corrections Director Mark Koderick testified at Davis' brief trial that contraband smuggling presented one of the biggest threats to prison security.

"The effects are not simply temporary highs," Shnider later added in a memo to the court, pointing to testimony from Koderick about seeing inmates undergo dangerous hallucinations, fainting, having seizures or harming themselves after ingesting such drugs.