Much like the differences in heroin from dealer to dealer, batch to batch, unique factors in the cases of three men originally accused of murder in three fatal heroin overdoses over the past year have resulted in different indictments handed up by a grand jury in each case.

The latest decision came Wednesday, when a grand jury decided not to indict Marc Roussel, 32, on a count of second-degree murder or manslaughter in the February overdose death of Guy Koontz. The grand jury did, however, indict Roussel on charges of possession of heroin and possession with the intent to distribute heroin. The latter charge carries a minimum penalty of 10 years in prison, up from a minimum of five before the legislature voted this spring to toughen penalties for heroin dealers at a time when heroin use has spiked nationwide.

The maximum penalty upon conviction of possession with the intent to distribute heroin remains 50 years for first-time offenders, as it was before the amendment was signed into law in May.

Although not charged with killing Koontz, Roussel still faces the possibility of more jail time than Brandon Eirick, 30, who in April was indicted on heroin possession and manslaughter charges in the December death of Leah Hutchinson.

A manslaughter conviction carries a maximum sentence of 40 years in prison.

Jarret J. McCasland, 24, was the only one of the three men arrested on a count of second-degree murder to be indicted by a grand jury on the same charge. A grand jury indicted McCasland in November in the July 2013 death of 19-year-old Flavia Cardenas. He faces a mandatory life sentence if convicted as charged.

Both McCasland and Eirick pleaded not guilty as charged at their respective arraignments.

“All of these are difficult cases,” said Hillar Moore III, East Baton Rouge Parish’s district attorney. “We’re just going to keep looking at them one by one.”

Moore said one potential weakness in the evidence against Roussel involves a pathologist’s finding that Koontz died with multiple drugs in his system.

Under the rarely cited provision of the state’s second-degree murder statute, the ingestion of some controlled dangerous substances, including heroin, must be the direct cause of death for a violation of the statute to occur.

Eirick told police that he did not directly inject Hutchinson, his girlfriend at the time, with heroin. Rather, she injected herself, he told them, marking a key difference between the case against him versus the case against McCasland, Moore has said.

A witness told authorities that McCasland injected Cardenas with heroin at her request because she did not know how to inject herself.

Although Roussel, the man indicted Wednesday on the drug charges, told police that he injected Koontz with heroin, the possibility that other drugs contributed to his death weakened the evidence attempting to connect Roussel to Koontz’s death.

So far this year, 15 people have died in East Baton Rouge Parish of a heroin overdose, said Dr. Beau Clark, the parish coroner, noting that some of those people may have had other drugs in their system.

“If heroin’s in the system, it is the one that kills you,” Clark said.

More than 30 people died of heroin overdoses in the parish last year, up from five the year before, reflecting the recent spike in heroin use throughout the area that also has been seen nationally. Local law enforcement agencies also reported large increases in the amount of heroin seized last year compared with 2012.

Authorities have not arrested any people other than Roussel, Eirick and McCasland on counts of second-degree murder in any of the other fatal overdoses in the parish.

Follow Ben Wallace on Twitter, @_BenWallace.