A burglary victim led police to the man who robbed her house by scratching him on the neck and trapping vital DNA evidence under her fingernails.
Annie-Laure Promonet, 42, from Watford, hatched her plan after discovering a man inside her flat trying to steal her laptop in July this year.
She tackled the burglar, tearing away his hoodie and digging her nails into his neck – collecting evidence that led police straight to serial offender Marvyn Mulvey, 40.
Jailing Mulvey for seven-and-a-half years on Friday, Deputy Circuit Judge Graham Arran praised Ms Promonet's bravery, saying she 'showed a very cool head'.
Annie-Laure Promonet, 42, from Watford, led police to burglar Marvyn Mulvey, 40, after scratching him on the neck to trap his DNA under her fingernails
French-born Ms Pomonet, who has lived in this country for 15 years, told the court how she fought with Mulvey after discovering him inside her flat on July 22.
Speaking outside court Ms Promonet, who works as an internal sales co-ordinator, said: 'Why did I do what I did? I think it was because I didn't have time to think.
'I had come home from the shops that afternoon and realised because I couldn't see my laptop that someone had been in my home.
'Then I heard a noise behind me and realised someone was in hallway of the building. I went out and he was making his way towards the front door with a bag. I just ran after him and grabbed him and pulled him back into my flat.
'I didn't have time to think that it was a dangerous thing to do. Maybe if I'd had just a few more seconds to think about it I wouldn't have done it, but I knew he had my laptop in the bag and I wanted to get it back.'
Prosecutor Richard Jones told the court that Ms Promonet succeeded in pulling Mulvey from the outside hallway back into her flat and to the kitchen.
He said 'negotiations' began with the brave householder pleading for the return of her laptop.
'She said he could have anything, but her laptop which was her life,' said Mr Jones.
He said a struggle then took place as Ms Promonet held onto Mulvey and the bag he was holding as best she could.
At one point Mulvey, who had been released from a previous prison sentence just days earlier, grabbed an empty wine bottle and used it to strike the woman over the back of the head and body.
The prosecutor said Ms Promonet continued to struggle with her attacker and realised the importance of gathering a trace of his DNA.
'She made it her aim to scratch him to obtain his DNA. She did that and was right,' said Mr Jones.
Ms Promonet told how she fought with Mulvey in the hallway of her Watford flat in July after discovering him inside trying to take her laptop
Deputy Circuit Judge Graham Arran jailed Mulvey for seven-and-a-half years at St Albans crown court on Friday while awarding Ms Promonet £350 for her bravery
The court heard Mulvey had chalked up 25 previous convictions and his first burglary conviction had been in 1992. Four years later he had been convicted of burglary with intent to rape and attempted rape.
He committed more burglaries over the years and in 2015 had been jailed for four years and six months for two offences of burglary, going equipped and escaping from lawful custody.
He had only just been released from that sentence when in July this year, homeless and penniless, he broke into Ms Promonet's flat.
The court was told that after fleeing from her home that afternoon, Mulvey had managed to find himself accommodation with the help of a homeless charity based in Rickmansworth Road in Watford.
But within weeks police had the results of the fingernail scrapings taken from Ms Promonet and a DNA match for Mulvey. He was soon traced and arrested.
In a letter to the judge Mulvey had penned, he told how he was sorry for what'd done and said 'Drugs and crime is all I have ever known.'
He said he was desperate to change his ways and added: 'I can only pray that poor lady recovers enough to put it all behind her. What I have put her though, no one should have to go though.'
On Friday he appeared at St Albans crown court and pleaded guilty to burgling Annie-Laure's ground floor flat in Watford town centre on the afternoon of July 22 this year as well as assaulting her occasioning her actual bodily harm.
He asked for 18 offences to be considered, 17 of which were residential break-ins.
Meanwhile the judge ruled that Ms Promonet should be given £350 out of public funds for her bravery.
She will be presented with her award at a ceremony at the crown court in the next few months.