Before the shooting, he had been identified by the site as one of more than 200 "baby butchers" across the United States who deserved to be punished as a mass murderer in much the same way that the Nazi leadership was tried at Nuremberg after the Second World War.
After the shooting, the website, called the Nuremberg Files, pointedly refused to express any regret about the violence. "Those who slaughter God's children without affording them due process of law need to understand they are going to be held accountable," it read. "Everybody gets a payday someday."
In the wake of Dr Slepian's death, a group of civil rights activists and pro-choice groups is now attempting to have the Nuremberg Files pulled off the web. As the three-week civil trial began in Portland, Oregon, plaintiffs argued that the site was an abuse of freedom of speech and a direct incitement to murder.
"Just like bounty hunters of the Old West, the defendants want to stop the doctors by any means - dead in their tracks," the plaintiffs' lawyer, Maria Vullo, said in her opening statement.
In an atmosphere of increasing intimidation and violence over the abortion issue in the United States, the Portland case could have far- reaching legal effects. The internet has made it easier for anti-abortion activists to pool information and post private details of their targets - including home addres-ses, phone numbers, details of family members, and so on - and led to a corresponding increase in fear among doctors who perform legal abortions.
In the Nuremberg Files, the names of practising doctors - as well as those of pro-choice judges, lawyers and politicians - appear in black. Those killed by anti-abortion activists over the past few years all have lines drawn through their names. The wounded appear in a ghoulish grey.
Ms Vullo described how some doctors on the list have taken to wearing bulletproof vests, vary their route to and from work, drive a variety of cars and have bulletproof glass installed in their homes. "It's terrorism, ladies and gentlemen, against people that do something the defendants disagree with," she said.
The defence argued it was merely participating in a political debate, and that its opinions were thus protected by the First Amendment of the US Constitution. "Opinion? Yes, sometimes harsh. But no violence," defence attorney Chris Ferrara argued.
The website is run by a computer scientist from Georgia. It features highly intemperate language about "slaughter ... that would have caused the Nazis to blanch" and graphic pictures of aborted foetuses "bagged like groceries destined for Satan's table". Hammer horror-style blood oozes from several of the website's banners.
The suit is aimed at a broader group of anti-abortionists, including the Portland-based Advocates for Life Ministries and the umbrella organisation American Coalition of Life Advocates. The plaintiffs hope not only to pull the plug on provocative websites but also to win a hefty financial settlement that will cripple the organisational ability of radical anti- abortionists.
A case in Chicago last year set a precedent favouring the plaintiffs' case against a group that refused to condemn violence by anti-abortionists. Earlier this week, in an unre-lated case, a Florida abortion clinic sued CompuServe and American Online for carrying online services enabling anti- abortionists to stalk abortion doctors and patients.