From behind bars, a Bucks County man appealing his conviction in a murder case plotted to kill a key witness in his retrial, prosecutors said.

Alfonso Sanchez, 39, has been charged with criminal solicitation to commit murder, conspiracy, witness intimidation and related offenses, court documents show. Prosecutors say he conspired with former inmates and others to track down and kill the witness, but the plot was foiled when his would-be accomplices contacted authorities.

In addition to the murder-for-hire plot, authorities say, Sanchez illegally smuggled narcotics into the Bucks County Correctional Facility over the course of several months last year. In that scheme, in which dozens of suboxone strips were brought into the jail in packages sent by mail, Sanchez was charged with operating a corrupt organization, possession with intent to deliver, conspiracy and related offenses.

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Sanchez’s attorneys in the murder case, Mark Eastburn and Francis Genovese, did not return a request for comment Monday. It’s unclear if they will represent him on these new criminal matters.

Bucks County District Attorney Matthew Weintraub said Monday that the new charges show that Sanchez “continues to demonstrate his utter disregard for the institutions we hold dear, for life and for the law.”

“In my professional experience, people that are factually innocent of the underlying crime they are accused of do not try to recruit others to kill witnesses against them,” Weintraub said.

Sanchez has been in custody since 2007, when, prosecutors say, he shot Lisa Marie Diaz, 27, and Mendez Thomas Jr., 22, in the head at point-blank range because Diaz owed him money for cocaine.

He was convicted of two counts of first-degree murder and sentenced to death, despite his attorney’s insistence that Diaz’s boyfriend, Steven Miranda, was the shooter.

Sanchez appealed his conviction, and prosecutors, while preparing to defend the appeal, discovered that in 2008, their predecessors had failed to turn over reports that DNA evidence found under Diaz’s fingernails matched Miranda’s.

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Despite that evidence, prosecutors maintained that Sanchez pulled the trigger. Still, Weintraub agreed in 2017 to a retrial.

While Sanchez was awaiting his new trial, prosecutors say, he hatched a plan to kill a witness to the shooting, according to the affidavit of probable cause for his arrest.

Investigators learned of the plot from former cellmates of Sanchez’s who became confidential informants. Detectives later intercepted phone calls and text messages between Sanchez and other alleged members of the Latin Kings street gang in which they discussed finding out where the witness lives and works, the affidavit said.

The witness — who was not identified by police — entered into a protection program, where she and her family remain, according to the affidavit.

» READ MORE: From 2007: "DA: 2 were killed over drug debt"

Also charged in the plot was Anthony Sparango, a friend of Sanchez’s, who authorities say told a confidential informant he planned to kill the witness and make the death look like a robbery gone wrong. Sparango also traveled with the informant around Warrington to scope out an apartment building where he believed the witness lived.

Sparango, 37, also faces criminal solicitation and conspiracy charges. He remained in custody Monday in lieu of $100,000 bail, court records show. There was no indication he had hired an attorney.

In the drug case, investigators say Sanchez directed an 11-member organization that smuggled suboxone into the Bucks County Correctional Facility through a binder of legal paperwork made to look like it had been sent by Sanchez’s federal defender.

As in the murder-for-hire plot, Sanchez’s role in the drug operation was discovered with the help of confidential informants, who clued investigators into how the drugs were entering the facility, authorities said.

In September, corrections officers at the jail intercepted a package sent to Sanchez that contained 91 suboxone strips with a street value of $18,000, the affidavit said.