Staff from the Genetic Identification department of Granada University have exposed a man who put someone else's saliva inside his mouth to fail a DNA paternity test.

Knowing that his ex-girlfriend's child was almost certainly his, the man, whose identity has not been confirmed, swallowed a pot of a friend's saliva moments before his sample was taken.

"The test gave an incongruous result. It's like writing something on a piece of paper, rubbing it out and writing over the top - you discover that the paper is not clean," explained laboratory director, José Antonio Lorente.

After performing the analysis a second time, the team realised that there were two people's DNA in the sample, and the man was forced to admit his deception.