"When illegal drug distribution causes a death, laws that were designed to punish the act are inadequate to recognize the seriousness of the resulting harm," Baker said.

His proposal aims to make traffickers who supply the substances that cause a person's death subject to prosecution for manslaughter, similar to the way the state treats someone whose decision to drive under the influence of alcohol or drugs leads to the death of another driver or pedestrian.

Amid an opioid crisis in the state, Baker's plan would create a mandatory minimum sentence of five years for anyone caught selling any drugs — not just opiates like heroin or fentanyl — that lead to a user's death.

Gov. Charlie Baker is targeting narcotics dealers with his latest opioid-related proposal that seeks to intensify criminal penalties for people found trafficking drugs connected to overdose deaths.

[Baker's] proposal aims to make traffickers who supply the substances that cause a person's death subject to prosecution for manslaughter.

The governor, who sits on President Trump's opioid task force, has created this bill after a year of working with the Legislature to try to stem the flow of opioids and improve addiction treatment options in Massachusetts.

Baker's bill, which offers a spectrum of additional proposals, also seeks to expedite the scheduling of new synthetic drugs.

The measure would link state drug classifications, with the exception of marijuana and already scheduled drugs, to emergency federal drug scheduling. The linkage would eliminate any lag time between the federal scheduling of new, synthetic drugs like Carfentanil and 251-NBOMe, known as "N-bomb," and state action to classify those drugs for prosecution.

The state would retain the right to change the classification of any drug. New Hampshire has already taken a similar step.

The other two tenets of the governor's bill deal with strengthening witness protection laws and making murder-for-hire plots a serious felony in the state.

Baker said loopholes were created under a 2006 rewrite of witness protection laws that, based on a 2011 court ruling, would allow someone to threaten harm to the child of their probation officer in retaliation for their supervision without facing a felony conviction.

The update Baker is recommending would extend witness protection laws to cover retaliatory conduct.

"While this may not be the result the Legislature intended in 2006, it remains the law of the Commonwealth today," the governor wrote.

Engaging in a murder-for-hire plot would also carry more serious penalties.

Currently treated as a misdemeanor in Massachusetts, solicitation to commit murder would become a felony in the state as it is in states like Maine and New Hampshire, where it is punishable by up to 30 years in prison.

Baker said the lack of such a punishment has led law enforcement in Massachusetts to request federal assistance in some murder-for-hire cases.

Positive signs in the state's fight against opioid addictions have emerged since the beginning of the year with 53 fewer people dying of opioid overdoses in the first six months of 2017, a 5 percent decrease from the same period last year.

"It is only through education, prevention, and treatment that, together, we will solve this public health crisis. Our focus must remain on these three pillars of our strategy. While maintaining that focus, however, we should also ensure that those who cause our citizens the most harm by illegally selling drugs that kill people are held accountable for their actions," Gov. Baker wrote in a bill filing letter to lawmakers.

Baker was to be joined by Lt. Gov. Karyn Polito, Secretary of Public Safety Daniel Bennett and advocates from the recovery, victim and survivor communities Wednesday afternoon at the Gavin Foundation's Devine Recovery Center in South Boston to introduce the new, four-pronged public safety bill.

The proposal comes as legislators are preparing to return from a summer recess after Labor Day for what House Speaker Robert DeLeo has promised to be a busy fall with criminal justice reform among the issues leadership wants to tackle.

Baker, in his filing letter, said his proposal draws from a number of ideas that are already pending before the Legislature in various bills filed this session.

With additional reporting from the WBUR Newsroom