Omondi had pleaded not guilty by reason of insanity, but a jury found him to be legally sane at the time of the murder.
Prosecutors say Omondi drowned the boy in a bathtub after discovering that his wages would be garnished to support his son and ex-wife.
According to the Orange County District Attorney's office, Richie Omondi moved from Kenya to the United States in 2002 to attend California State University, Fullerton.
Two years later his wife and young son, Richie Omondi joined him. Struggling to support his family, Omondi wanted to send his wife and child back to Kenya, but when his wife refused, Omondi filed for divorce. The two then were granted joint custody.
Prosecutors say a close call came first on Jan. 6, 2006, when Omondi became angry after a family court hearing, and drove his son to a desolate stretch of highway near Bakersfield. Prosecutors say he doused the trunk of his BMW with gasoline and locked himself and his son in the trunk with matches in his pocket. But a passing California Highway Patrol stopped and opened the trunk. Omondi said the two were sleeping and the officer let them go.
Finally, on Sept. 10, 2006, Omondi had his 4-year-old Richie for the weekend, when at approximately 7:00 p.m., prosecutors say Omondi filled up his bathtub in his Fullerton apartment and intentionally drowned Richie.
According to the allegations, Omondi then put his son's lifeless body on a bed, and two hours later drove to the Fullerton Police Department where he turned himself in.
During the sentencing, Richie's mother, Hellen Mwangi, gave a tearful victim impact statement, telling the court that her only son had wanted to be a fireman. She called Omondi a monster for taking away Richie's young life. She said that Omondi cared more about his education than he did about his own son.