Detecting malingering begins with a search for over-exaggeration, contradictions and inconsistencies. For example, you might suspect someone’s credibility if they report debilitating auditory hallucinations but seem unperturbed by them. Beware the bank robber who describes seeing “a 30ft-tall, red giant smashing down the walls” with remarkable composure. Another red flag for fakery is the suspect who endorses improbable symptoms, such as agreeing with the question, “Have you ever believed that automobiles are members of an organised religion?”

Malingerers often claim to have lost touch with reality. But their hallucinations can seem too convenient with “psychotic justification”, as seen with the man charged with attempted rape who alleged a voice told him to “Go commit a sex offence” or the thief who claimed a mystery voice screamed, “Stick up, stick up, stick up!”

There are some other differences physicians can look for in episodes of genuine versus faked psychosis.

In genuine psychosis, auditory hallucinations are usually intermittent (even if there’s a sense they’re always hovering in the background) and patients can sometimes resist commands if they’re not acutely unwell. In contrast, malingerers frequently report continuous hallucinations and say they’re compelled to follow all instructions. People with genuine hallucinations typically report that the voices are repetitive and identifiable, both male and female (in three quarters of patients), speak the same language as themselves (in 98% of patients) and originate in their own heads (in 88%). Conversely, here’s an atypical presentation of voice hearing: unidentifiable voices of just one gender (or a gender that changes mid-sentence), only a child’s voice, or a voice that sounds like a robot or animal. These atypical features raise suspicion for malingering but don’t confirm it.

Reports of visual hallucinations carry similar clues. In schizophrenia these are usually in colour and life-sized (religious figures, family members, animals) but malingerers instead tend to report exaggerated details: “I just saw Big Bird.... He was 100ft tall!” There are exceptions, though. Patients in alcohol withdrawal or with macular degeneration or schizophrenia can hallucinate Lilliputian figures (small animals or people). Here’s one authentic description from a 25-year-old drinker: “They were about a foot high, with funny colourful dresses, weird faces, big eyes and mouths. Some of them were also wearing spectacles.”

So even with these general rules of thumb, pinpointing genuine psychosis remains challenging. A single feature cannot confirm malingering; instead each one points, in the right context, towards the possibility. It’s also vital not to presume malingering and miss an authentic mental health disorder – not to mention that both can co-exist.