A search for a religion with 'more morals' than the Catholicism she was raised in led Katherine Russell, 24, the widow of Boston bomber Tamerlan Tsarnaev, to convert to Islam, her husband's former friend has revealed.

According to the Boston Globe, retiree Donald Larking, 67, commenced an unlikely friendship with Tamerlan in 2011 when the Boston bomber was 25 and his mother Zubeidat Tsarnaev had begun caring for Larking's quadriplegic wife in their home just west of the city.

'She wanted a church with more morals,' Larking told the Globe. 'She felt that a mosque would be a safer place for her daughter to go to nursery school.'

Larking, who is himself a convert from Catholicism to Islam, met Tsarnaev's wife when Zubeidat Tsarnaev returned to Russia last year. When Zubediat left the country for good Katherine Tsarnaev reportedly took over the role of carer to Larking’s wife.

Speaking to the Globe, Larking claimed that Tsarnaev admitted she had become disillusioned with the Catholic Church following the series of international sexual abuse scandals that engulfed it in recent decades.

Russell, 24, was described by the Globe as an all-American girl when she began dating Tsarnaev. Soon she converted to Islam, then dropped out of her studies at Sussex University in Boston before graduating to marry the then promising boxer in a ceremony in 2010.

Friends in her hometown of North Kingstown, Rhode Island, told the Daily Mail that the woman they knew 'was brainwashed by her super-religious husband.' After meeting Tsarnaev she was 'not the same person at all,' they claimed.

Meanwhile Larking, who suffers from mental and physical disabilities from a gun shot to the head in a convenience store robbery in 1974, described his friend as 'Very very religious. He believed that the Koran was the one true word and he loved it.'

After the bombings Tsarnaev reportedly quit the Cambridge, Massachusetts apartment in which she and her husband had lived, to return to her emergency physician father Warren and nurse mother Judith, along with her younger sisters Rebecca, 22, and Anna, 19.

Tsarnaev and her 3-year-old daughter Zahara have been living in the Rhode Island home since her husband was killed in a police shootout on 19 April.

Now out of the shadow of her controlling husband friends say that she has started listening to rock music and painting her nails, neither of which her husband permitted.

Amato DeLuca, one of Tsarnaev's lawyers told MailOnline that despite reverting to her maiden name, Katherine remains a devout follower of Islam.

The Globe reports that about a year ago, Tsarnaev handed his Irish American landlord Joanna Herlihy a copy of the notoriously anti-semitic tract The Protocol of the Elders of Zion, which describes a plan by Jewish leaders to take over the world. It was first published in Russia over a century ago and has inspired generations of far right extremists.

Herlihy said she warned Tsarnaev that the book was seen as 'propaganda.' Still, she admitted she had tried to 'plow through it' over the winter, although she admits she couldn't finish it. Now she claims she feels bad that she missed an opportunity to confront him and his increasingly extreme ideas.

'I’ve regretted it,' she said told the Globe.

Katherine Russell (24), the widow of Boston bomber Tamerlan Tsarnaev, converted from Catholicism to IslamGoogle Images