San Mateo police Detective Rick Decker testified that he was among the first investigators to search the two-story town home on Casa De Campo that Youshock shared with his mother and sister in the hours after the attack occurred.
Youshock is on trial for two counts of attempted murder, one count of using of explosives in an act of terrorism and other charges related to two pipe bombs he allegedly set off as classes began at about 8 a.m. on Aug. 24, 2009.
Prosecutors allege that Youshock went to the school intending to kill his former chemistry teacher, bringing with him homemade pipe bombs, a Samurai sword, and a chainsaw he nicknamed "Collie," after Columbine High School, the site of the infamous 1999 massacre.
When investigators were collecting evidence from Youshock's bedroom, they found a digital photo of Youshock holding the chainsaw, with the caption "Collie hates you more than I do."
Numerous other photos and about 15 minutes of video that Youshock filmed of himself holding swords, mixing ingredients for bombs, exploding test bombs, and reading from his "manifesto" -- in which he says "You had your chance to avoid this day, but you chose to oppress me. Now it is my turn to be the oppressor" -- were found on a thumb drive on Youshock's disheveled bed, Decker said.
Also recovered from the bedroom were at least four versions of the manifesto handwritten on folded pieces of paper that were hidden inside a stereo speaker. Chief Deputy District Attorney Karen Guidotti asked Decker to read them to the courtroom.
"'I bring upon you the misery you gave me. You called this upon yourselves,'" he said.
Youshock shifted in his chair when the detective read from the scribbled pages.
Along with the manifesto drafts was a collection of receipts from various purchases made over the past two years, Decker said.
The receipts chronicled purchases of charcoal powder and fine sulfur powder from eBay, a hockey bag from Big 5 Sporting Goods, a wrench, galvanized pipe, PVC pipe, six pipe fittings, four doorstops and a chainsaw from Home Depot.
In a downstairs patio storage room, investigators found a cottage cheese container filled with crystal powder, chains, a hatchet, a propane stove and a tennis ball that was filled with match heads to create an improvised explosive.
The prosecution alleges that the evidence points to a months-long premeditated attack that Youshock planned in order to kill a teacher who had flunked him.
Defense attorney Jonathan McDougall maintains that the defendant suffers from schizophrenia, which causes paranoia and prevents him from discerning reality from fantasy.