Nicolas Holzer — the 45-year-old man who allegedly stabbed his parents, two sons, and family dog to death with kitchen knives in their Noleta home last summer — pleaded Tuesday not guilty by reason of insanity. Judge Brian Hill appointed psychiatric doctors David Fennell and Brandon Yakush to the case, which had slowed the case’s progress for several months. The doctors are expected to return to court in about five weeks to report the findings of their evaluation. Holzer faces four counts of first-degree murder and one count of animal cruelty. He is scheduled to return to court on December 1.