A mother stabbed by her neighbour as her teenage son tried to fend him off died today, police said.
James Killen, 18, went to help his mother Sandra Crawford during the attack at their home in St Albans, Hertfordshire, on April 30.
James fatally stabbed Jonathan London, 46, after he launched the violent attack on Ms Crawford.
Ms Crawford, 53, was taken to Addenbrookes Hospital in Cambridge after the attack at the home she shared with her son on Sherwood Avenue.
At the time her teenage son was arrested on suspicion of murdering Mr London but was later released on police bail.
Sources said the investigation seemed to indicate he had stepped in to defend his mother.
Today Ms Crawford died from her injuries, Hertfordshire Police said.
Detective Chief Inspector Melanie Burn, who is leading the investigation in to the attack, said: "This is an extremely tragic case and our thoughts are with Sandra's family at this exceptionally sad and distressing time.
"Our primary concern has been to seek a balanced and fair outcome in this matter. The legal process must run its course, however we are hoping to resolve this matter as quickly as possible to allow Sandra's family to grieve and start to rebuild their lives."
In a statement, Ms Crawford's family said: "Sandra was a much loved mother, daughter, partner and friend.
"We are currently coping with the traumatic events of her death and we respectfully request to be left alone at this time."