Although Flannagan evaded police for a time, both sisters were caught and convicted of one of the murders; they were both hanged on the same day at Kirkdale Prison.

In 1880, unmarried sisters Catherine and Margaret Flannagan[note 1] ran a rooming house at 5 Skirving Street in Liverpool.

His death did not raise any particular comment; Catherine collected £71 (worth roughly £7120 in 2019 pounds) from the burial society with which he had been registered and he was interred shortly thereafter.

[3] When Patrick discovered that his brother has been insured with five different burial societies,[1] which left his widow with a profit of around £100,[2][3] he pursued the matter with the authorities.

[3] Evidence from the home, including "a bottle containing a mystery white substance and a market pocket worn by [Margaret]"[1] was examined by poison expert Dr Campbell Brown, who verified the presence of arsenic – dust in Margaret's pocket, and an arsenic solution (containing unusual adulterants) in the bottle.

[1] Orders for the exhumation of the previously deceased members of the household were issued when it became clear that arsenic was the mechanism of Higgins's death.

[4] Catherine's list of alleged conspirators contained three poisoners other than herself, one accomplice, and three agents of the insuring groups who had provided payouts upon the deaths.

[4] Ultimately it was decided by the prosecuting solicitor for Liverpool that while the additional deaths were likely to be murder, it would be difficult to prove that anyone other than Catherine or Margaret had committed them, especially considering that the primary evidence against the other women was being provided by Flannagan, who had every reason to attempt to minimise her own responsibility in such crimes.

[8] Modern accounts of the sisters, such as those by Angela Brabin[5] and the television series Deadly Women,[9] have focused more on the cooperative aspect of the crimes rather than the poison aspect, and tend to refer to them as "black widows" or "The Black Widows of Liverpool", particularly in reference to the allegation that the Flannagan sisters were part of a larger murder ring.

[4] A radio dramatization of the murders and following events titled Life Assurance, written by Chrissie Gittens based on the book The Black Widows of Liverpool by Angela Brabin (Palatine Books, 2003 ISBN 978-1-874181-21-7/2nd Revised Edition 2009 ISBN 978-1874181606) and directed by Claire Grove, was broadcast on BBC Radio 4 in 2005, with Sorcha Cusack as Catherine Flanagan, Gillian Kearney as Ellen Flanagan, Anny Tobin as Margaret Higgins, Robert Hastie as Inspector Keighley, Stephen Hogan as Thomas Higgins, Hugh Dickson as Dr. Whitford and Nicholas Boulton as Patrick Jennings.