Partners who suspect their spouses of cheating are often drawn to shifty warning signs like staying out later, changing phone habits and increased secrecy.
But British private investigator Paul Jones of ARF Investigators has warned that there is one tell-tale sign, often overlooked by suspicious spouses, that could be a clear indication of adultery.
Even something as unlikely as a toothbrush could hold information that incriminates an adulterous partner, the investigator, who has more than a decade of experience catching love rats, told The Mirror.
It's rare to actually catch a cheater red handed, but cautious parties should watch closely for 'small clues' lurking in 'innocent' places.
These could be as seemingly insignificant as 'spending more time at work, picking up a new hobby or taking more pride in their appearance', he explained.
Proving infidelity is about culminating 'data', and this could even be in something as little as monitoring teeth brushing habits.
Paul recalled one case of a mother who had suspected her husband was cheating on her.
At the time, she had installed a smart electric toothbrush app in the hopes of encouraging her children to improve their brushing habits.
The app, which was used by everyone in the family, tracked every single session of dental care.
'Over time, the client noticed their partner's brushing history was being logged at odd times, times when they were supposedly at work,' Paul explained.
'At first, it didn't seem like much, brushing late in the morning on Fridays didn't raise immediate red flags.'
Monitoring the app, the mother could see that her husband had been brushing his teeth at home during periods that he'd been claiming he was at work.
It revealed that he had been brushing his teeth later in the mornings on Fridays, a time when he was supposed to be out the house.
In reality, her husband hadn't worked a single Friday in three months, and had been having an affair with one of his work colleagues in their family home.
Knowing the whole house would be out on Fridays, her husband had secretly been inviting his mistress over, all the while pretending he was at work.
Rather than looking in the more obvious places, in texts, emails and note apps, suspicious partners will more often than not find clues in the most mundane of places.
Even smart devices like voice assistants and toothbrushes can hold incriminating information about cheating partners. Though partners can lie, data doesn't.
As Paul said: 'It's timestamped, often location-based, and emotionless. When a device says someone brushed their teeth at 10:48 am when they were supposed to start work at 9 am that's very hard to explain away.'
He urged suspicious partners to search for 'digital cues', which can be 'as innocent as a toothbrush'.
It's not the only place where signs of cheating could lurk. London-based private investigator Aaron Bond of detective agency Bond Rees said there is one app rarely checked by partners, that could prove vital to determining whether someone is having an affair.
Instead of heading straight to WhatsApp, the notes app, or camera roll, Bond has urged concerned spouses to check the supermarket loyalty scheme apps, such as Tesco's Clubcard.
He told The Mirror: 'While most people think of text messaging and call logs as the obvious signs of cheating, there are often other signs that can uncover and paint a larger picture'.
Bond said that while most people would never consider browsing the receipts of their partner's Clubcard use, it can be incredibly revealing.
The private detective, who has helped people catch their unfaithful partners for over 15 years, said there are 'digital signals' to weed out white lies from suspecting cheaters.
Supermarket loyalty cards, used to help shoppers save cash and earn rewards, are rarely thought of as a place to stash secrets. Indeed, few shoppers are aware that apps are even tracking them.
However, according to the private investigator, the often-overlooked loyalty apps contain all manner of data that could help pick out a cheater.
'Clubcard data is limited, but it does tell you a date and location which is easily accessible if you log into your account,' he said.
For example, if an individual is dubious about what their partner has really been up to, they can verify their location and purchases made using the app.
'If your partner claims they were working or out with friends but the account shows they made a purchase in a completely different area then it’s a clear red flag,' Bond explained.
While Clubcards can't offer a definitive answer as to whether someone is being unfaithful, monitoring historic purchases and spending habits to line up with a suspicious partner's alleged activity can help reveal whether they are lying about what they're up to.