At about 06:45 on 28 March, police arrived at Andrey Perlov’s house near Novosibirsk in Siberia.

They accused him of stealing about three million roubles ($32,000; £24,000) from a Novosibirsk football club where he was the managing director - he and his family deny this.

Perlov, who is 62, is an Olympic gold medallist, having won the 50km race walk in 1992.

He has been detained for more than six months and his family says he is being pressured to agree to fight in Ukraine. He’s been told that, in return, the embezzlement case against him would be frozen and potentially dropped when the war ends.

It’s no secret that prisoners have been recruited to fight in Ukraine, but BBC analysis can reveal how the initial focus on convicted criminals has shifted to include people yet to face trial.

The latest laws mean that both prosecution and defence lawyers are now legally obliged to inform people who are charged with most crimes that they have the option to go to war instead of court.

The legislation, passed in March 2024, means that if they sign up, the prosecution and any investigation will be stopped. Their cases will generally be closed completely at the end of the war.

“This has turned Russia’s law enforcement system upside down,” says Olga Romanova, the director of Russia Behind Bars - an NGO that provides legal assistance to detainees.

“Police can now catch a man over the corpse of someone he has just killed. They tighten the handcuffs and then the killer says: ‘Oh wait, I want to go on a special military operation,’ and they close the criminal case.”

We received a leaked recording of an investigator describing the advantages of signing a contract with the Russian army to someone whose husband had already been sentenced to three years for theft.

“He can get six more for this other crime,” he tells her. “I offered him a chance to sign an agreement. If his request is approved, he will go to war and we will close the case.”

If the accused signs, within a few days the criminal case is suspended, and they leave for the front line almost immediately.

Three lawyers working in Russia confirmed that this has become the norm across the country.

Some sign up in the hope of avoiding prison and a criminal record - but it’s not an easy way out, as teenager Yaroslav Lipavsky discovered.

He signed a contract with the army after he was accused of intentionally inflicting "serious harm to health by a group of persons by prior agreement”.

His young girlfriend had just found out she was pregnant and in order to avoid prosecution, Lipavsky signed up with the military as soon as he turned 18.

He left for Ukraine and a week later was dead - one of the youngest soldiers to die in the war.

It’s not clear how many people accused of crimes have opted to fight instead of facing trial, but this shift in policy reflects Russia’s need to reinforce troops while minimising the number of other civilians it needs to mobilise.

“Do Russians care about convicts or those who are in prison? I suspect that they don't,” says Michael Koffman, military analyst at the Carnegie Endowment for International Peace.

He thinks the government “likely assumes that these are people they can lose, that nobody will miss and that they will not have a substantial, negative effect on the overall economy”.

When the Wagner mercenary group first recruited prison inmates, its late leader, Yevgeny Prigozhin, targeted convicts in high-security jails, saying he needed their “criminal talents” in return for pardons.

The BBC and Russian website Mediazona have seen and verified confidential documents that shed light on the process of recruiting prisoners, what has happened to many of them and the need to maintain the flow of new fighters.

We know, from analysing the dog tags of convicts who died in Ukraine and payments made to their families, that Wagner recruited nearly 50,000 inmates from penal colonies, and at one point were losing up to 200 in action every day. Many others were injured.

All prisoners’ dog tags start with the letter K, which stands for “kolonya” or prison colony.

The first three numbers identify the prison where they came from and the last three numbers identify the recruit, given out in sequence - so the higher the number, the more recruits came from that colony.

Payment records show that more than 17,000 prisoners were killed trying to capture the city of Bakhmut in eastern Ukraine between July 2022 and June 2023 alone.

To plug the losses, Wagner, and later the Ministry of Defence, have adapted their recruitment strategies to broaden the pool of people they can draw on.

Some people accused of crimes refuse the new deal because they are against the war in principle, others because the risk of dying or being injured on the battlefield is too great, and others because they want to stay at home to fight their case.

But they can come under huge pressure from the authorities, says Andrey Perlov's daughter Alina.

“He refused and we made quite a big noise in the local media so he was sent to the strict punishment cell, where they brought him the contract again."

She adds that when he refused a second time, he was forbidden from seeing or calling his family.

They still hope to prove his innocence, but the last time Alina saw her father in court in mid-July, he had lost a lot of weight. “He tries to keep himself cheerful,” she says, “but if this goes on, they will break him.”

We asked the Russian authorities about Andrey Perlov's case and whether they are unfairly pressurising detainees to join the army. They did not respond.