A jury will continue deliberating murder charges against Nathaniel Fujita of Wayland, after the panel of eight men and four women was unable to reach a verdict Wednesday in Middlesex Superior Court. Fujita, 20, is accused of beating, strangling, and slashing to death his former high school sweetheart Lauren Astley on July 3, 2011, and then dumping her body in a marsh. Fujita’s defense attorney has argued that his client was psychotic at the time of the killing. Prosecutors are seeking a first-degree murder conviction, which carries a life sentence without parole, but the jury is also allowed to consider a second-degree charge, which carries a life sentence with the possibility of parole after 15 years. If Fujita is found not guilty because of a lack of criminal responsibility, he could be evaluated or committed at a mental health hospital. Fujita’s trial lasted about three weeks; Wednesday was the first full day of deliberations.