The court-appointed monitor overseeing New York City's jails is concerned that guards are striking too many inmates in the head.

Steve Martin's second report since being appointed a year ago was filed in Manhattan federal court Monday.

Martin reviewed 1,700 records documenting uses of force at Rikers Island between March 1 and July 31 of this year.

He found about 235 incidents that involved a blow to an inmate's head and another 300 that involved an inmate in restraints.

Blows to the head are supposed to be used only as a last resort because they can be fatal.

Martin found guards used force about a quarter of the time after inmates refused to follow a direct order.

Martin says jail violence remains high. He says reform efforts will take hold in time.