Polaroid photographs were taken of Tina Karuthasami, 38, after she was attacked by her boyfriend at the home they shared in St Albans, Hertfordshire. Darren Simmonds, 30, was given a six-week sentence for the assault.
Ms Karuthasami gave a statement to police about the incident on 6 February, but withdrew it a week later. However, Crown Prosecution Service lawyers decided to prosecute on the evidence of the photographs alone.
St Albans Crown Court was told that the couple had been drinking vodka at their home when a struggle broke out during which Ms Karuthasami scratched Simmonds' left cheek and right jaw. Simmonds squeezed her throat and pushed her away roughly, causing her to fall and be injured.
Simmonds, who admitted causing actual bodily harm, accepted he was responsible for the injuries visible in the photographs. The court was told that the three photographs showed severe bruising to Ms Karuthasami's face and right cheek, her left cheek was swollen and there were fingernail and hand marks on her neck.
Sentencing Simmonds to six weeks' imprisonment, with half suspended, Judge Gareth Davies said drink was no excuse for domestic violence.
He said: "The real seriousness of this offence is the extent of the injuries shown in the three photographs which I have seen. They show clearly the extent of force used. The offence is so serious only a custodial sentence is justified."
Afterwards Detective Chief Inspector Adrian Tapp, of Hertfordshire police, said: "This is the first time in British legal history that a Polaroid photograph has been used in a case of this nature and has been so influential in securing a conviction."