A perpetrator can also say the condom came off by accident.
When it is explicitly said that the sex is only consented to on the condition that a condom is worn, the non-consensual removal of the prophylactic means that it is no longer consensual sex - it's rape.
In the recent "stealthing" case, which is believed to be the first of it's kind in New Zealand, a specific prostitution law may have added strength to the prosecutor's case.
In the case's summary of facts, Judge Stephen Harrop told the court defendant Jessie Campos was made aware that a condom was legally required during the sexual contact at the start of the one-hour session, and multiple times throughout.
As a sex worker, the woman and her client, were required under section 9 of the Prostitution Reform Act to take reasonable steps to ensure a condom or another appropriate barrier was used.
This would have made defending the man's actions harder as there is a legal requirement for one to be worn during the encounter, which he had been made aware of multiple times.
But with sexual activities where no money changes hands there is no inherent contract demanding protection is used - making it difficult for victims to prove stealthing has occurred.
University of Waikato law lecturer Paulette Benton-Greig said that while the law under the PRA doesn't fundamentally change anything about the offending, it is much easier to demonstrate that a person knew they had to wear a condom if there is a legal obligation to do it.
Although once there is a precedent that a jury is willing to convict on, the Crown is more likely to proceed with similar cases, she said some prosecutors may believe conviction was only possible because of the law in the PRA.
"And [say that it] doesn't necessarily mean a jury will convict in absence of that."
One woman spoken to by the Herald said she had been told by police that they may have been able to do "something" about her stealthing case if she had been a sex worker.
Besides being against the law, there are significant physical risks of this stealthing - including pregnancy and STIs, and significant emotional harm to the victim-survivor.
Victoria University of Wellington's Dr Samantha Keane said although the recent conviction will undoubtedly help raise awareness about the impacts of "stealthing", she told the Herald it won't always be easy to secure convictions in these cases.
"When sexual violence occurs, it is not typically in the presence of other witnesses, so many cases become scenarios of 'he said vs she said'.
"Of cases that do make it to the attention of Police, we know that attrition is high and not all cases will make it to court. Of those that do, sexual violence cases have a lower conviction rate than for other offences."
Since news of the first conviction broke in April, a police spokesperson said they weren't aware of any increases in reports of this type of offending.
Police records don't distinguish this sort of assault from sexual offending generally.
Benton-Greig believed there needed to be a change in attitude from authorities so that they take the risk and prosecute stealthing cases.
"They just need to kind of go a step further and take a case in which the complainant was really clear that the use of a condom was discussed and consent was conditional of that, and he knew that and for a jury to be willing to convict."
