SANTA ANA, Calif. – A transient man has been charged for the stabbing murder of an acquaintance on a bike path in Irvine. Dennis Thomas Monson Jr., 37, is charged with one felony count of murder with a sentencing enhancement allegation for the personal use of a knife. If convicted, Monson faces a maximum sentence of 26 years to life in state prison. Monson was charged today and is scheduled to be arraigned on Friday, April 1, 2016, at 10:00 a.m. in Department CJ-1, Central Jail, Santa Ana.

At the time of the crime, Monson was a transient and was acquainted with 51-year-old Sidney Siemensma.

During the early morning hours on Jan. 19, 2016, Monson is accused of getting into a verbal argument with Siemensma on the San Diego Creek bike trail in Irvine. During the course of the argument, Monson is accused of stabbing the victim multiple times with a knife. Siemensma died at the scene as a result of his injuries.

A jogger on the trail contacted the Irvine Police Department (IPD) to report an injured man bleeding on the trail.

At approximately 7:20 p.m. on Jan.19, 2016, an IPD officer patrolling near the trial located, contacted, and searched the defendant. Monson is accused of possessing images depicting minors in a sexually explicit manner on his cell phone. Monson was subsequently arrested by IPD.

IPD investigated these cases.

Monson was charged on Jan. 21, 2016, with one felony count of possession and control of child pornography (Case #16HF0099). If convicted, the defendant faces a maximum sentence of three years in state prison. Monson is scheduled for a pre-trial hearing on May 16, 2016, at 8:30 a.m. in Department C-49, Central Justice Center. Deputy District Attorney Michael Carroll of the Sexual Assault Unit is prosecuting that case.

Assistant Head of Court Howard Gundy of the Homicide Unit is prosecuting case #16HF0427.

*Defendant also has an open child pornography case

Orange County District Attorney / Case # 16HF0427 & 16HF0099 / March 29, 2016