Three Leicestershire Police officers are being investigated by the police watchdog for their contact with Valdo Calocane before he killed three people in Nottingham.
Two police constables and a sergeant may face charges of potential misconduct regarding how they investigated an earlier case against Calocane.
Barnaby Webber (19), Grace O'Malley-Kumar (19), and Ian Coates (65) were fatally stabbed in Nottingham on June 13, 2023. While Webber and Kumar were Nottingham University students, Coates was a caretaker at Huntingdon Academy.
The force had referred itself to the Independent Office for Police Conduct (IOPC), after it was found that officers were investigating Calocane's alleged assault of two colleagues on May 5 at a warehouse in Kegworth, Leicestershire.
Investigators are looking at what information was available to police about Calocane before the triple murder.
The police claimed that nobody was seriously hurt, and Calocane was escorted off by the security guards before they reached the spot.
The IOPC is also examining Nottinghamshire Police's decisions and actions relating to Calocane between September 2021 and June 2023.
The police watchdog said it would also probe how the force informed the families of the death of their loved ones and the subsequent support they provided them. This includes how they were informed about the ongoing investigation.
Senior officers are also being probed to see whether relevant policies were followed. All Nottinghamshire officers are currently being treated as witnesses, the IOPC said.
The watchdog is separately examining several complaints made by the Nottingham victims' families.
Calocane was sentenced to detention in a high-security hospital after admitting manslaughter on the grounds of diminished responsibility.
His guilty pleas were accepted after medical evidence showed he had paranoid schizophrenia.
During his sentencing, a judge told Calocane that he would probably be detained in a high-security hospital for the rest of his life.
The families of the attack victims expressed their anger after the killer was given the hospital order.
A review launched by the attorney general earlier this year found the sentence was not unduly lenient.
Curator Emma Slocombe with ikat robes and arabachi coats in the Peter the Great Room in Blickling Hall Amit Roy 
View of the entrance to Blickling Hall on a rainy autumn dayAmit Roy 
Kente cloth from Ghana in the Long Gallery in Blickling Hall 
Decoration in the Great Hall at Blickling Hall Amit Roy 
Palampore fragment made in coastal south-east India in the Brown Room in Blickling Hall Amit Roy 
Bed valance dating from early 1700s in the Italian Print Room at Blickling Hall Amit Roy 
Indian inspired fabric draped on sofas in the South Drawing Room in Blickling Hall Amit Roy 
Indian inspired fabric draped on sofas in the South Drawing Room with Indian carpet in Blickling Hall Amit Roy 
Karun Thakar has picked out the geometric patterns in the bookcase and the Kente cloth in the Long Gallery in Blickling Hall Amit Roy 
Large tapestry depicting Peter the Great defeating the Swedish army at the Battle of Poltava in 1709 Amit Roy 
ikat robes and arabachi coats in the Peter the Great Room in Blickling Hall Amit Roy 
Baghs and kanthas made by women provide contrast to the men only portraits in the Great Hall at Blickling Hall Amit Roy 
Baghs and kanthas in the entrance Great Hall at Blickling Hall Amit Roy
Baghs and Kanthas in the Great Hall in harmony with stained glass window at Blickling Hall Amit Roy 
Kimonos reflect Japanese influence in Upper Ante Room in Blickling Hall Amit Roy 
Kimono in Upper Ante Room in Blickling Hall 
A view of the Palace and fort at Agra shows romantic side of India Amit Roy 
Blickling Hall Amit Roy 
Table carpet, European 1670-1680 Amit Roy 
Unfinished 17th century Italian embroidery in the Print Room at Blickling Hall Amit Roy 
Picture of Kashmir shows a romantic view of India Amit Roy 
A panel of Ashburnham bed hangings made in Gujarat for sale in Europe in the Brown Room in Blickling Hall Amit Roy 
Colcha made in the 1600s by women in Bengal for the Portuguese market in the Long Gallery at Blickling Hall Amit Roy
