Daniel Carr, 37, and daughters Tammy, 15, and Sabrina, 14, were also cleared of the manslaughter of Lisa Greenway. Tammy Carr, who stabbed Lisa, was found guilty of manslaughter on grounds of provocation and sentenced to four years youth custody.
Mr Carr, who was alleged to have goaded his two daughters into the attack, and Sabrina, were cleared of manslaughter on the grounds of provocation. Mr Carr and Sabrina, who are facing an unconnected charge of wounding, were released on bail.
Lisa, of Freasley Road, Shard End, Birmingham, died in hospital shortly after the attack during a row between two groups of youngsters in the Castle Bromwich district of Birmingham in February this year.
Sentencing Tammy, Mr Justice McCullough said: 'I fully accept the guilt you have felt . . . and have taken into account the great strain these proceedings must have been to you. I know you are a girl of good character, a girl of immense potential as well.' But the offence was so serious 'that only a custodial sentence is justified - a term of substantial length.'
During the two-week trial the prosecution alleged that Mr Carr encouraged his daughters in the fatal attack and was described by one witness as 'looking like a referee at a wrestling match'.
Neither Mr Carr nor Sabrina gave evidence but Tammy told the court that she first tried to pull her younger sister and Lisa apart because they were fighting. She used a knife to 'prod' Lisa and only meant to frighten her.
She said: 'I prodded her two or three times and then I did it harder. I did not want to cause her serious injury. I was scared.'
Roger Smith QC, for the prosecution, told the jury that the attack appeared to stem from a dispute between two groups of young people after Sabrina had allegedly called one of Lisa's friends 'a slag'. Lisa was knifed in the legs, buttocks and back.
As the verdicts were announced all three accused cried and Mr Carr hugged his daughters.
David Crigman QC, defending Tammy, said she recognised the enormity of what she had done and did not wish to minimise the impact of what happened 'one iota'. Mr Crigman told the court: 'The loss of life in this case has presented a most enormous burden for a 15-year-old girl to carry and there have been times when it has been almost impossible for her to deal with it.' He said she had since suffered from nightmares and 'flashbacks'.Reuse content