NEW YORK (CBSNewYork/AP) — The court-appointed monitor overseeing the jails of New York City 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 U.S. District Court in Manhattan on Monday.

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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.

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

In 2014, a report indicated that nearly a third of Rikers Island inmates who said their visible injuries came at the hands of a correction officer in the two years before had suffered a blow to the head.

The report, prepared by New York City health department officials, found 8,557 verified injuries among Rikers’ inmates between April 2012 and April 2013. Of those, 1,257 injuries allegedly resulted from use-of-force by corrections officers. The rest were attributed primarily to inmate-on-inmate violence. It classified 304 of the injuries as serious, meaning they were fractures or other injuries that required more than first-aid treatment.

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

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