Forensic staff who are members of NIPSA have begun industrial action
Crime scene investigators, who gather forensic evidence to help Northern Ireland police catch criminals, have begun industrial action.
The dispute is over how much they are paid to be on call to work evenings and weekends.
Some work for the PSNI and others for the Forensic Science Agency. They provide similar services but those within the PSNI are paid less.
The teams will refuse to work 'on call' rotas until the dispute is settled.
The scientific staff working for the PSNI want equal payment.
The trade union NIPSA, which represents about 120 of the 140 forensic staff, said PSNI employees who attend crime scenes should receive similar allowances as their colleagues employed by Forensic Science NI.
A NIPSA spokesman said they had started industrial action at 12:00 GMT on Friday.
