Saliva found on a victim's T-shirt's after a fight involving N-Dubz star Dappy has a ''billion-to-one'' chance of not being his, a court has heard.

The 'Bad Intentions' rapper has been appearing at Guildford Crown Court in Surrey, South East England, this week regarding a ''mob attack'' last February - during which he is accused of insulting and spitting at two girls before proceeding to hit onlooker David Jenkins.

Although the spittle missed the two 18-year-old girls, forensic scientist in the case Carolyn Smith told the court that saliva belonging to Dappy - whose real name is Costadinos Contostavlos - had been detected on David's top.

She explained : ''We estimated the probability of getting this DNA profile from another person who was unrelated to Mr. Contostavlos as one in a billion.''

The jury was told yesterday (09.01.13) the 25-year-old musician put David in a ''headlock'' when he stepped in to defend Grace Cochran and Serena Burton.

Paul Greaney, defending Dappy, asked Ms. Smith whether the saliva could have been wiped on to the item of clothing after or during the headlock, to which she replied: ''It could have been that way, there are numerous options.''

The incident took place at a Shell garage on Woodbridge Road, Guildford, in the early hours of the morning on February 28, 2011, when Dappy and his alleged accomplices Kalonji David Stewart, Kieran Vassell and Alfred Miller stopped for some petrol.

During their stop Dappy tried to convince the two girls to get into his car, turning nasty when they refused - calling them ''sl*ts'' and one ''ugly''.

When David stepped in it is said to have ''all kicked off''.

Taxi driver Tahir Jaffrey told the jury he saw a group fighting when he pulled into the station, recalling: ''I do not want to see violence, I just called police when I saw it happen. I saw these three guys and all of a sudden people came out of their cars and began fighting.

''I do not know how this fighting started. It was very quick what I saw.''

Dappy denies two counts of common assault on the two women, one of assault by beating, of David, and one of affray.

Kalonji and Kieran deny charges of affray, while Alfred Miller admitted to committing affray and is to be sentenced after the trial.