Mixed European Court ruling in Russia Khodorkovsky case
The European Court of Human Rights has ruled that Russian officials violated the rights of jailed tycoon Mikhail Khodorkovsky, but the court rejected his claim that his trial was political.
The judgment from Strasbourg is similar to one issued by the court in May 2011 concerning the former Yukos oil boss, who was once the richest man in Russia.
This time Russia was ordered to pay him 10,000 euros (£8,600) in damages.
But the judges ruled that the case against him had a "healthy core".
His case was considered together with that of his business partner Platon Lebedev.
Khodorkovsky was arrested in 2003 and convicted of tax fraud in 2005 .
In 2010 he was convicted in a second case of stealing oil from his own company.
His 13-year sentence is running concurrently with his first and will keep him in jail until 2016.
Through his lawyers Khodorkovsky has maintained that the case against him was trumped-up to block his support for liberal groups opposed to Vladimir Putin, who was serving his first presidential term at the time.
The BBC's Daniel Sandford in Moscow says both sides will claim victory in this case.
The judges said Khodorkovsky's rights were breached because he was sent to a penal colony far from Moscow, and because among other things the defence was not allowed to bring its own experts as witnesses.
But the court said that the trial judge was not biased, and that Khodorkovsky may well have been guilty of tax evasion.
It said "some government officials had their own reasons" to push for his prosecution, but that did not make the prosecution illegitimate "from start to finish", which was Khodorkovsky's allegation.
The ruling can still be amended by the Grand Chamber of the ECHR in Strasbourg.
The ECHR ruling in 2011 related to the start of legal proceedings against Khodorkovsky and Lebedev, whereas Thursday's ruling concerned their criminal prosecution, which resulted in them being found guilty of large-scale tax evasion and fraud in 2005.