Carpenter was born and raised in San Francisco, California. His father was an abusive alcoholic and his mother was very domineering and also abused him. By the age of seven, he was stuttering so badly that it was impossible for him to socialize. As a result, he was often teased. He was also forced to take part in extracurricular activities such as ballet and violin lessons, which only led to more teasing. Later, he wet the bed and engaged in animal torture, two of the three indicators of the MacDonald Triad. At the age of 17, he was jailed for molesting two of his younger cousins. Released after only a year, he continued molesting children until he got married in 1955 and had three children, Michael David, Gabrielle Louise and Circe Anne. Over the years, Carpenter made a living working various jobs, including as a salesman and as a printer. He also did some service in the Coast Guard, from which he was honorably discharged. Though Carpenter constantly demanded sex from his wife, he continued stalking women. In 1960, Carpenter befriended a woman and lured her into the woods in Presidio, where he bound her with a clothesline, beat her with a hammer and stabbed her in the hand. Luckily, a military patrol officer caught him in the act. Carpenter fired at him with a gun, but missed and was injured by return fire and arrested.
The next year, Carpenter was sentenced to a total of 14 years in prison for one count of assault with intent to commit murder and two counts of assault with a deadly weapon. While he was serving his sentence, his wife divorced him and he was found by the prison psychiatrists to have sociopathic personality disorder and an IQ of 125. He was released after serving only nine years and quickly remarried, though his second marriage also failed. From the end of January until the beginning of February, he committed a series of attacks against women. On January 27 all in one day, he forced a woman out of her car by hitting it with his own and tried to rape her. Though he stabbed her, she got away and was able to remember his license plate number. He then broke into another woman's home, kidnapped her, raped her and stole her car. On February 3, he stole a woman's car and then raped another woman. Her infant child was present during the attack and was treated well by Carpenter, who was arrested the same day. While awaiting trial, he tried to escape along with four other inmates, but was caught quickly. He made a plea bargain and was convicted of robbery and kidnapping. Not long after he was paroled to a federal halfway house in May of 1979, he is believed to have escalated to murder. While he was committing murders, Carpenter took courses in computer printing at the California Trade School. After getting his degree, he got a job as a typesetter instructor.
Killings, Arrest and IncarcerationCarpenter's first suspected victim was 44-year-old Edda Kane, who went hiking in the Mount Tamalpais State Park on August 19. She was found the next day, shot in the back of the head with a .44. In September, Carpenter was released from the halfway house and moved in with his parents. On October 21, he stabbed Mary Frances Bennett to death, a crime he wasn't connected to until decades later. He didn't kill again until March the following year, when he stabbed Barbara Schwartz, who was walking her dog. A witness saw the whole attack, ran for help and gave the rangers a description of the attackers, though it later turned out to have been wrong. When a pair of prison issue glasses were found at the crime scene, investigators looked for suspects among convicted sex offenders, but found no good leads. Meanwhile, Carpenter, who had been injured during the attack, claimed to have been injured during a robbery. He bought a new pair of glasses for himself, but because he didn't fit the description, he wasn't suspected. In October, Carpenter killed Anne Alderson, who went jogging in the woods. In late November, Carpenter claimed another victim, Shauna May, raping and killing her and leaving her near the body of another victim, Diana O'Connell. A further search uncovered the bodies of a murdered couple, Rick Stowers and Cindy Moreland. By now, people were becoming aware that a predator was active in the area and were warned to stay away from nature paths.
Presumably in order to change his M.O., Carptenter lured his last known victim, Heather Scaggs, by arranging with her to sell her a used car. After her disappearance, the investigators, now a multi-agency task force consisting of local law enforcement as well as FBI, took an interest in Carpenter due to his connection to the victim and prior sex offenses; he hadn't shown up in prior searches of released sex offenders because he was technically serving a federal sentence even though he was free. When Carpenter was arrested, the investigators searched his car and found several guides to local hiking trails. They also later recovered the .38 Carpenter used in his killings, which he had left with a friend. There were also several witnesses who placed him and his car at the locations of several attacks. On May 24, the body of Heather Scaggs was found hidden under some bushes. Of the then eight murders attributed to Carpenter, he wasn't charged with those of Edda Kane and Barbara Schwartz due to a lack of evidence and wasn't charged with the murder of Heather Scaggs. Put on trial, Carpenter was found guilty of the first-degree murders of Rick Stowers, Cindy Moreland, Anne Alderson, Diana O'Connell and Shauna May and was sentenced to be executed via gas chamber. In 2009, San Francisco police reexamined evidence from the 1979 murder of Mary Frances Bennett and connected her death to Carpenter with DNA evidence. He remains on the San Quentin death row to this day (June 2017). At the age of 87, he is the oldest member there.
Carpenter primarily targeted young women who were hiking in the woods. After subduing them with a blitz attack, he would kill them either by shooting them with a .44 or .38 handgun execution-style or by stabbing them with an unknown bladed instrument, sometimes also binding them with wire or clothesline. During his later murders, he would also rape his female victims.
John Douglas's profile of the Trailside Killer said that he would be familiar with the area, which means he is a local, but he is shy, reclusive, and may have a speech impediment. Contrary to what the local psychologists had decided (that the offender was charming, sophisticated, and good-looking), Douglas thought that he would instead be unsure of himself in social situations. He chose victims of opportunity rather than focus on a certain victimology. He is white and intelligent with a blue-collar job and had spent time in jail. His M.O. was simply to approach his victims from behind, if possible, and become aggressive to overwhelm them. He would have a history of at least two of the three background indicators of psychopathy: fire-starting, bed-wetting, and cruelty to animals. However, Douglas also thought the killer was probably in his thirties and had recently experienced some precipitating stressors.
- Unspecified date in 1947: His two unnamed cousins, 8 and 3 (molested only)
- Unspecified dates in 1948 to 1955: Numerous unnamed children (all molested only)
- July 1960:
- Lois DeAndrade (attempted; bound, stabbed in the hand, and struck six times on the head with a hammer)
- Officer Wayne Hicks (attempted to shoot)
- January 27:
- Cheryl Lynn Smith (attempted; stabbed and stripped; she escaped)
- Wilma Joyce (last name undisclosed; abducted and raped; survived)
- January 29: Sharon O'Donnell (held at gunpoint; escaped)
- February 3: Barbara (last name undisclosed; abducted and raped, but not killed)
- January 27:
- August 19: Edda Kane, 44 (shot once in the back of the head with a .44)
- October 21: Mary Frances Bennett, 23 (stabbed)
- March 8: Barbara Schwartz, 23 (stabbed 12 times in the chest with a boning knife)
- October 11: Rick Stowers and Cindy Moreland (confirmed; both were shot in the head)
- Richard "Rick" Stowers, 19
- Cindy Moreland, 18
- October 15: Anne Alderson, 26 (confirmed; raped and shot in the head with a .38)
- November 28:
- Diana O'Connell, 22 (confirmed; raped, strangled, and shot once in the head)
- Shauna May, 25 (confirmed; raped, bound with wire, and shot three times in the head)
- March 29: Ellen Hanson and Stephen Haertle
- Ellen Hanson, 20 (shot with a .38)
- Stephen Haertle (attempted; severely injured, but escaped)
- May 2: Heather Scaggs, 20 (raped and fatally shot through the eye with a .38)
- March 29: Ellen Hanson and Stephen Haertle
- For a while, Carpenter was a suspect of being the Zodiac Killer, but was cleared since he was in jail during at least one of the confirmed murders and his handwriting and fingerprints didn't match that of the case evidence.
On Criminal Minds
- Season One
- "Extreme Aggressor" and "Compulsion" - While not directly mentioned or referenced in Season One, Carpenter may have been an inspiration for The Footpath Killer - Both were serial killers with similar nicknames, had severe stutters, attacked their victims in the wilderness, and used blitz-attacks to subdue them before shooting them in the head.
- Season Three