HALIFAX -- The Nova Scotia prosecution service has dropped charges against an 81-year-old woman best known for killing and poisoning her intimate partners.

Melissa Shepard -- often referred to as the Internet black widow -- was released from prison in March after serving a full sentence of just under three years for spiking newlywed husband Fred Weeks's coffee with tranquilizers in 2012.

In April, she was charged with violating court release conditions by allegedly using a computer at the Halifax Central Library. An Internet ban had been one of several conditions placed upon her, based on her prior record of using the web to meet men.

But on Thursday, a Crown spokeswoman said prosecutors had determined there wasn't a reasonable prospect of convicting Shepard and withdrew the breach of conditions charges against her on Tuesday.

"The Crown is obligated to halt the prosecution when such a determination is made," said Crown spokeswoman Chris Hansen.

However, Shepard remains bound by 21 peace bond conditions, which continue to prohibit her from using the Internet, and require her to report weekly to police and to inform authorities of potential relationships with men.

The peace bond conditions will continue for two years regardless of this week's decision by the Crown to drop the latest charges.

Hansen said the public can rest assured that the long list of peace bond conditions will provide unusual levels of protection aimed at preventing any further crimes by Shepard.

"The peace bond is in place since Nov. 23 of this year. It carries with it strict conditions that should assure the public that Ms. Shepard is of little or no risk to the public," she said.

The trial on the charges against Shepard of breaching conditions had originally been scheduled for Feb. 1, and is now cancelled.

Shepard has a long criminal record extending across the continent.

In 1991, she was convicted of manslaughter and served two years of a six-year prison term after killing her husband Gordon Stewart on a deserted road near Halifax.

Stewart, from P.E.I., was heavily drugged when Shepard ran over him twice with a car.

Shortly after she was released from prison, she travelled to Florida and met Robert Friedrich at a Christian retreat. They married in Nova Scotia in 2000.

A year later, Friedrich's family noticed his health faltering. He had mysterious fainting spells and slurred speech and was in and out of hospitals.

In 2005, Shepard was sentenced to five years in prison for a slew of charges stemming from a relationship she had with another Florida man she met online.

She pleaded guilty to seven charges, including three counts of grand theft from a person 65 years or older, two counts of forgery and two counts of using a forged document.

Shepard's lawyer, Mark Knox, was not immediately available for comment Thursday.