Imagine being able to place a suspect at a crime scene, simply by later looking for the telltale signs in their brainwaves.
It's not technology that's beyond the horizon, but already in use in some countries - and it could soon prove a handy tool for police in New Zealand.
What's called forensic brainwave analysis (FBA), or simply "brain fingerprinting", measures involuntary brainwave responses that reveal whether a person recognises particular information.
The testing process uses an EEG machine to measure certain brainwave responses.
The person being tested selects various pre-loaded images, sentences and phrases on a computer screen.
By interpreting the pattern of these brainwaves, the tester can establish if the person tested has knowledge of particular information.
"So, police might have 10 possible suspects and not be sure where to go from there; this can eliminate five to six of those, allowing them to focus their time and money on a smaller number, which certainly suggests there's more chance they'll get a successful outcome," said Associate Professor Debra Wilson, of the University of Canterbury.
While the technology could not read a suspect's mind, as it were, it could confirm they were at the scene of the crime, whether they perpetrated it or not.
Wilson, along with her colleague Professor Robin Palmer and US-based brain fingerprinting pioneer Dr Larry Farwell, have just completed a year-long, NZ Law Foundation-backed research project exploring the concept.
It has been used successfully in tests and court cases in the US to help prove both guilt and innocence, and by police in India at the investigation stages of several cases.
"There's quite a big legal debate over whether this could be admissible in court, or whether you could use it as evidence to convict someone," Wilson said.
"We are not sure about that - but it's definitely got a use in just helping police with their investigations."
In the New Zealand project, the team also worked with police and corrections staff, using supervised student researchers to carry out experiments to observe, test, analyse and verify the technology.
"The project team's overall conclusion was that the verification experiment results provide a solid platform for further research into FBA technology, towards the goal of applying it in police investigations and the New Zealand legal system," Palmer said.
Canterbury Police District Commander Superintendent John Price said his officers found participation in the project "a very valuable experience".
"We are encouraged by the potential of this technology to assist in forensic investigations in the future," Price said.
"We have a strong partnership with University of Canterbury and welcome any opportunity to improve the safety of our community through improved research and knowledge based policing."
Law Foundation executive director Lynda Hagen said the foundation was pleased to have supported the research.
"Brain fingerprinting is just one of many exciting new technologies with potential to transform the law and legal process."
The researchers will be discussing the project, which also addressed related legal and ethical rights, and potential cultural issues, at a public seminar at Canterbury University on August 2.