Two legal cases dealing with the rights of family members to decide life or death for a critically injured loved one have touched off a storm of controversy on both sides of the Atlantic, landing one mother in prison for life, and locking a young couple in battle with the very doctors charged with keeping their infant alive.

In East London, England, 57-year-old Frances Inglis’ self-confessed mercy killing of her 22-year-old son Thomas, who doctors said would live the rest of his life in a vegetative state after a catastrophic accident, made headlines when courts ruled her act was murder and sentenced her to life in prison.

On the other side of the Atlantic, in Edmonton, Canada, a young couple is engaged in a life-and-death court fight, trying to keep doctors from essentially doing the same thing to their infant son who suffered brain damage.

While there's an ocean separating these two cases, the same question applies to both: Who should have the authority to decide whether another person lives or dies? And does any one person have the right to decide whether someone else's life isn't worth living?

Experts say it is a complex issue that involves legal and ethical questions.

Inglis' son, Thomas, sustained serious head injuries after he jumped out of a moving ambulance in July 2007. He went into a vegetative state, but was not terminally ill. Two months after his injury, Inglis injected her son with an overdose of heroin. But nurses resuscitated him -- and she was charged with attempted murder. One year later, while out on bail, Inglis successfully administered the heroin overdose and killed her son.

In Canada, Isaiah May was born in October 2009 with his umbilical cord wrapped around his neck. He was deprived of oxygen, and had inhaled amniotic fluid and fecal matter. Isaiah is still alive; he requires a ventilator to breathe, and he is fed through a tube.

Doctors, who by Canadian law have the right to pull the plug, say Isaiah has no hope of getting better. But the baby's parents Isaac and Rebecka May, took the hospital to court and won a temporary extension. The Mays are waiting for another doctor to perform an independent assessment on their son.

"I think there are times when euthanasia may be justified," says Dr. Rosamond Rhodes, a professor of medical education and director of bioethics education at Mount Sinai School of Medicine in New York City.

"The case of Francis Inglis is clearly a case of euthanasia from her point of view," she told "She (Inglis) saw it as a benefit to her son. She saw that ending the life of her son would be better than allowing it to continue. And for a great personal sacrifice, she was willing to do this for her son."

Rhodes said it could be seen as an "extreme offense to personal dignity to be kept alive in that type of condition."

"In terms of quality of life, if someone is actually experiencing only pain with no foreseeable alleviation of the pain or improvement and no meaningful interaction of the world… you can say for them… ending their life is a benefit. You can make that argument," Rhodes said.

On the other hand, Rhodes does not believe the Canadian case has anything to do with euthanasia.

"For the parents, they’re saying, ‘for my baby to continue life,’ is a benefit to them and they don’t want to end it," Rhodes said. "While the hospital is saying he will never recover, and it’s clearly a medical fact that they have established.

"Certainly if the parents have machines in their home and are bearing the burden and expenses, then it’s their decision. But they’re asking the state to provide the care. It’s a legitimate question of social justice. The state only has so many resources."

Dr. Keith Ablow, a psychiatrist and Fox News contributor, said individuals should not be given the power to decide life and death, because it will ultimately be misused.

"If individuals can decide independently when enough is enough, and life should end, then we would be on a very slippery slope indeed," Ablow said. "(What about) parents of paralyzed children who see them face so many daunting obstacles in life, would they conclude their lives should end? What about mentally retarded individuals?"

As a psychiatrist, Ablow said, he wonders if Inglis had a motive other than ending her son’s suffering, "including her own desire to be done with the admittedly excruciating journey of visiting him in the hospital and seeing him so damaged."

Perhaps in the past, Inglis also felt her life was hopeless or not worth living, Ablow said.

On the other hand, Ablow said that the Canadian couple – Isaac and Rebecka May – are "demonstrating tremendous psychological strength in lobbying for their baby Isaiah to continue life-sustaining treatment. …No doctor can predict with absolute certainty that some level of recovery is not possible."

If these cases were being presented in America, the law is pretty clear-cut as to what would happen, said Judge Andrew Napolitano, Fox News’ senior judicial analyst .

Only two states — Oregon and Washington — have Death by Dignity Acts, which allow a person to be euthanized — and only if two physicians certify the person knows what they are doing and they agree the person’s case is terminal.

Since Thomas Inglis was in a vegetative state and could not express whether he wished to live or die, his mother would have been charged with murder in the U.S., Napolitano said.

Frances Inglis could have withheld extraordinary assistance -- breathing machines and nourishment -- if two or more doctors agreed that Thomas would not come out of his vegetative state, but "in no states can you affirmatively end the life of a person in a persistent vegetative state," Napolitano said.

In the case of the Mays, the hospital would have to abide by the parents’ wishes, since they are the next of kin.

"In this country, the consent of the guardian is an absolute necessity," Napolitano said. "If the hospital says yes, and the guardian says no, the patient stays on life support."

Napolitano says the Canadian case is political, because health care is paid for by the government, and the government most likely does not want to pay for Isaiah’s care any longer.

Click here to read more about the May's story.

Click here to read more about Frances Inglis' story.