A convicted Ohio man on death row is expected to become the first person in the United States to be executed with a lethal, single-drug injection.<br/><br/>Kenneth Biros, 51, was sentenced to death for the murder of a 22-year-old woman in 1991.<br/><br/>Ohio is the first US state to adopt the new method using a dose of thiopental sodium instead of a drug combination.<br/><br/>The change of approach follows a failed attempt to execute a prisoner in Ohio in September, when officials struggled for two hours to try to find a suitable vein into which to inject the drugs.<br/><br/>All executions were put on hold while another method was sought.<br/><br/>Critics say the method, which may take twice as long to take effect, is human experimentation. Officials deny that.<br/>