Amanda Knox and her Italian former boyfriend were found guilty last night of the murder of the British student Meredith Kercher, who was stabbed to death two years ago.

Knox, 22 and Raffaele Sollecito, 25, killed Kercher in an attack which ended with Sollecito taunting Kercher with one knife while Knox plunged another into her throat, the court heard during the trial.

Kercher, 21, from Coulsdon, Surrey, was found with a deep knife wound in the throat on the floor of her bedroom in the flat she shared with Knox and two young Italian women. She was a student at Leeds University and was spending a year at Perugia's university for foreigners when she was found murdered on 2 November 2007.

Knox, who came into the courtroom weeping and shaking, appeared not to react immediately as the sentences were read out, but then broke down and buried herself in the shoulder of her senior lawyer, Luciano Ghirga. She was led from the court by police and her sobbing could be heard from the corridor that leads away from the vaulted underground court in which the trial has been heard.

Her younger sister, Deanna, 20 wept. Sollecito, who had been less composed than his former girlfriend during the trial, sat rigidly, staring ahead as the colour drained from his face. His stepmother was seized by a panic attack and appeared to be hyperventilating.

Knox was sentenced to 26 years in prison while Sollecito was sentenced to 25 years. Knox was also found guilty of several other offences including criminal slander for pointing the finger of guilt at Diya "Patrick" Lumumba, 38, who ran a local bar. He later proved to have an alibi and was released after initially being arrested in connection with the murder.

Knox's family left court in tears and fought their way through the dense crowd. Asked if he would fight on, Curt Knox, the American student's father, replied: "Hell, yes."

Kercher's family's lawyer, Francesco Maresca, said they were satisfied with the verdict. He said: "They got the justice they were expecting. We got what we were hoping for."

The verdict put an end, though perhaps only a temporary one, to a case that has baffled and divided amateur detectives on both sides of the Atlantic and turned a probing light on the Italian legal system. Knox, a student at the University of Washington, and her boyfriend were sent for trial despite the fact that a third person had been convicted of the killing before their indictment. Rudy Guede, a drifter born in the Ivory Coast, was sentenced to 30 years last year after a fast-track trial. He is appealing against his conviction.

Last night's verdict will almost certainly prompt another appeal as Knox and Sollecito, a computer science graduate, try to establish their innocence in a higher court. They were caught up in the murder inquiry after investigators became suspicious of their behaviour in the hours and days following the discovery of Kercher's body.

The two former lovers gave contradictory accounts of their movements on the night of the crime when, as they both acknowledged, they had been smoking cannabis. Amanda Knox then gave police a statement which she subsequently retracted, in which she said she had been at the flat when Kercher was murdered and had covered her ears to block out her screams. Her statement, at the end of an overnight without the assistance of either a lawyer or interpreter, interrogation was ruled inadmissible by Italy's highest court.

But, by a quirk of the law, it was able to be cited repeatedly in court and even shown this week on a giant screen to the two professional and six lay judges trying the case. That was not the only unusual aspect of a trial during which the leading counsel for the prosecution, Giuliano Mignini, was being tried for abusing his powers in another case.

Mignini, who initially suggested Kercher might have died in an occult rite, later argued that Knox had killed her because she had come to hate her British flatmate. The judges appeared to have accepted that explanation and the prosection's reconstruction of the killing, which also changed during the trial.

This had Sollecito taunting Kercher with one knife while Knox plunged another into her throat. Mignini suggested it was culmination of a violent game forced on the British student in which she was sexually assaulted by Guede.

The final days of the trial saw media sentiment in Italy shift in favour of the defendants as their lawyers kept up an offensive on the forensic evidence linking them to the crime.

On Thursday, Knox and her former boyfriend both made emotional appeals to the judges to free them, but to no avail. The US student and the young Italian had spent more than two years in jail waiting to know their fate. Trials in Italy proceed at a leisurely pace of, at most, two hearings a week and this one took eight months.