No ricin was found during a search of the Mississippi home of the man charged with sending letters tainted with the toxic substance to US President Barack Obama and a US senator, an FBI agent has testified.
Agent Brandon Grant also told a federal judge in Oxford, Mississippi, that investigators found no trace of the deadly poison in defendant Paul Kevin Curtis's, pictured, vehicle, his ex-wife's home or his parents' house.
Mr Curtis (45) faces a maximum of 15 years in prison if convicted. His attorney, Christi McCoy, has argued that all the evidence against her client was circumstantial unless he could be linked to the ricin.
Ms McCoy raised the possibility that Mr Curtis was being framed by a man recently arrested on child molestation charges with whom Mr Curtis had a long-running e-mail feud.