A convicted rapist could make a bid for early release after winning an appeal in which judges ruled that lying to a sexual partner about being infertile is not rape.

Jason Lawrance, a serial sexual attacker who is serving a number of life sentences, was found guilty last July of raping a woman twice after lying to her about having had a vasectomy.

But the convictions for raping the woman – who became pregnant and had an abortion – were quashed on Thursday by appeal court judges who said they were unsafe.

Lawrance’s solicitor, Shaun Draycott, said: “There was real concern that the upholding of the convictions recorded at Nottingham crown court [last July] would have had the potential to criminalise large sections of an otherwise law-abiding population, both male and female.

“The ruling provides clarity on the important issue of whether one person’s consent to a sexual act can be negated by another person’s dishonesty.”

Lawrance’s legal team did not appeal against his other convictions but Draycott said they would have to consider whether the ruling could potentially impact on the tariffs that relate to his life sentence.

The self-employed builder contacted thousands of women on the dating app Match.com and attacked a dozen women between 2009 and 2014.

Lawrance, from Liphook in Hampshire, was convicted in 2016 of raping five women and of sexually assaulting and attempting to rape two others. Jailing him for life, a judge described him as “devious, manipulative and highly dangerous to women”.

Lawrance, originally from Leicestershire, went on trial again last July accused of raping and sexually assaulting six more women. One of these was the woman he deceived about having had a vasectomy. They had consensual sex but he sent her a text the day after sleeping with her, saying: “I have a confession. I’m still fertile. Sorry.”

Under the Sexual Offences Act 2003, a person commits rape if the other “does not consent to the penetration” or they “do not reasonably believe” the person consents.

Katie Russell, a spokesperson for Rape Crisis England and Wales, said the act was clear that an individual must have both capacity and freedom in order to make a choice about whether to consent to a sexual act.

“This means they mustn’t be constrained in any way in their decision-making. The law recognises too that consent can be conditional, ie someone might consent to sex with but not without contraception.”

In the case of Lawrance, she said his lie “led to significant, likely traumatic physical and emotional consequences for the complainant”.

“We must better recognise and understand the meaning of genuine consent in our society, not only for the sake of criminal justice for sexual violence and abuse survivors, but also to reduce and prevent sexual offences and promote healthier, more respectful attitudes to sex in general,” she said.

In their ruling on Thursday, the court of appeal judges said: “In terms of section 74 of the 2003 act, the complainant [the woman] was not deprived by the appellant’s [Lawrance’s] lie of the freedom to choose whether to have the sexual intercourse which occurred.”

They considered other cases, including Julian Assange’s extradition case – in which a judgment said that sex without a condom would be an offence in Britain if the other person had agreed to intercourse only on the condition of one being used – and another known as R(F) involving a woman who consented to sex with her husband on condition that he withdrew before ejaculating.

“Unlike the woman in Assange, or in R(F), the complainant agreed to sexual intercourse with the appellant without imposing any physical restrictions,” said the ruling by the lord chief justice for England and Wales, Lord Burnett of Maldon, along with Mrs Justice Cutts and Mrs Justice Tipples. “She agreed both to penetration of her vagina and to ejaculation without the protection of a condom.”

They added: “The deception was one which related not to the physical performance of the sexual act but to risks or consequences associated with it.”