This is one of the chilling ‘selfies’ a female serial killer formerly from Harpenden took while she was on the run that were shown to a jury this week.

Joanna Dennehy, 31, who reportedly attended Roundwood Park School, has admitted stabbing three men in the heart and dumping their bodies in ditches.

Victims Lukasz Slaboszewski, 31, Kevin Lee, 48, and John Chapman, 56, were found left by fields outside Peterborough in March and April last year.

According to her sister, who spoke to a national newspaper after Dennehy gave her guilty plea last year, she left their £315,000 four-bedroom family home in the St Albans district aged 15 and got in with the wrong crowd.

Despite murdering the three men, Dennehy remained ‘unsatisfied’ and fled to Hereford in search of more victims, the Crown says.

She cruised the city and selected two other men at random, stabbing Robin Bereza, 64, and John Rogers, 56, who survived the cold-blooded attacks.

Alleged conspirators Gary Stretch, 47, and Leslie Layton, 37, who are now on trial, deny helping to cover up the “terrible truth” of the murders.

Pictures of Dennehy and Stretch were shown to Cambridge Crown Court as Mark Lloyd, an associate of Gary Stretch, and Georgina Page, a friend of the triple killer, gave evidence on Monday.

The shocking images include one of Dennehy jovially sticking her tongue out as she brandishes a jagged knife with handcuffs attached to her jeans.

As the pictures were shown to the jury, Mr Lloyd revealed he had been forced to watch on helplessly as she tried to kill two strangers in Hereford.

He recalled the moment the murderer leapt out and stabbed Mr Bereza, who was walking his dog, ‘like a scene from Psycho’.

He said: “She takes a knife out of her left pocket with her right hand.

“She strikes him like in the film Psycho, just like that. Thrusting and putting her whole weight behind it.

“I just kept saying ‘what the f*** is going on, I haven’t signed up for this’.

“Gary is seeing exactly what I’m seeing and there’s just no emotion from him at all.”

A picture of the knife believed to be used in all five attacks was also shown to the court and described as a nine-inch fold knife.

Mr Lloyd said he saw the same knife in Dennehy’s hands at a flat in Hereford occupied by his friend Moby.

It was there that Dennehy took pictures of herself and Stretch as they prepared to drive round the city in a bid to kill again.

Mr Lloyd told the jury that the blade “was as black as the handle” because of all the congealed blood and that it “smelt like copper”.

He said Dennehy than told him: “I’ve killed three people, Gary’s helped dispose of them and I want to do some more.

“You’ve had your fun Gary, I want my fun.”

Dennehy, of Orton Goldhay, Peterborough, pleaded guilty to the three murders and two attempted murders at the Old Bailey in November.

She also admitted preventing the lawful and decent burial of all three victims and is in custody awaiting sentencing.

Stretch, of Orton Goldhay, real name Gary Richards, denies three counts of preventing the lawful and decent burial of a body and two counts of attempted murder.

Leslie Layton, 37, of Orton Goldhay, denies two counts of preventing the lawful and decent burial of a body and one count of perverting the course of justice.

A third man Robert Moore, 56, of Peterborough, has admitted assisting an offender and is awaiting sentence.

The trial of Stretch and Layton continues.