A few months before Alan J. Smith is alleged to have killed his estranged wife, he Googled information about forensics and evidence, and ordered a season of the TV show “Forensic Files,” according to prosecutors.

Smith’s Internet searches in the winter of 2012 included questions about the realism of “CSI: Miami“ and other crime shows, how long DNA tests take and how to obtain fake passports, Snohomish County prosecutors wrote in documents used Friday to charge Smith with first-degree murder in connection with the Feb. 11 slaying of Susann Smith, 37.

Around the same time, Alan Smith ordered an entire season of “Forensic Files” from his Net­flix account, prosecutors wrote in the court documents.

The evidence was collected from his work computer, iPad and cellphone, prosecutors said.

Susann Smith was struck 22 times in the face and head, possibly with a rubber mallet and another weapon that has not been identified, before she drowned in the bathtub of her Bothell home, according to the autopsy. Her facial injuries were so severe that dental records were needed to identify her, police said.

According to court documents, the couple were in the midst of an acrimonious divorce, and Alan Smith feared his estranged wife would return to Germany and take the couple’s two children with her.

He was ordered held in lieu of $1 million bail during his arraignment Monday in Snohomish County Superior Court.

According to court documents, Smith, 38, had become increasingly bitter after his estranged wife’s parenting plan was accepted by a court commissioner, and he began to tell co-workers that the courts were rigged to favor women and designed to drain his bank account.

One co-worker, who described Smith’s behavior over the past year as a “descent into madness,” said he ranted obsessively about his estranged wife.

Prosecutors said in charging documents that Smith began planning the attack months before the slaying and made extensive efforts to cover his tracks.

He talked to a former girlfriend about making people “disappear” and about how a rubber mallet could inflict injuries without leaving bruises, prosecutors said. That former girlfriend told police she’d seen a rubber mallet among Smith’s possessions last year, according to the documents.

Prosecutors say the mallet has not been found.

Smith’s financial records also show that he purchased a bicycle last fall, according to prosecutors. Surveillance video of the route between Susann Smith’s home and his apartment, about 2 miles away, shows a lone bicyclist riding in the direction of the victim’s house at 2:24 a.m. on Feb. 11, the day her body was found. The same video shows a lone bicyclist heading back toward Smith’s home less than two hours later, court documents allege.

Prosecutors say a witness reported seeing the bike Smith had bought, left unlocked and unattended at a local grocery, at a nearby hotel and in a greenbelt near the apartments where Smith was living. Investigators, who seized the bike, said in court documents they believe Smith was hoping the bike would be stolen.

Court documents also say that police found chemical-resistant coveralls and disposable gloves in Smith’s car.

Smith moved back into the Bothell home in April, saying he planned to seek custody of the couple’s children, 3 and 6, who had been taken into Child Protective Services, neighbors told Bothell Reporter in May.

Police were called to the home several times in the weeks that followed. In one instance, Smith’s girlfriend was sunbathing nude in the backyard. In another, police responded after a neighbor heard a scream and found Smith and his girlfriend having sex in the semi-enclosed front yard.

Court documents also say detectives said that Smith, who was arrested on investigation of murder on June 27, tearfully answered a question about the slaying, posed by a leader at his church, by saying, “Yes, I did it to her.”

Investigators said in the court documents that the church leader claimed he was not acting as a clergyman during the conversation, and that he went to police when Smith did not turn himself in.

Christine Clarridge can be reached at cclarridge@seattletimes.com or 206-464-8983.