Barasat: Three under trials inflicted injuries on themselves inside the prison van on way to Barasat court from Dum Dum Central jail in North 24 Parganas district.
Police said the three inflicted superficial injuries on their hands with a sharp artefact, perhaps a pen.
While the exact reason was yet to be known, police said it could be just a show.
The three have been taken to a hospital here. The trio were arrested in 2009 from Baguihati in the district for peddling drugs.