Marty holds a doctorate in law from the University of Neuchâtel. His thesis was entitled, The Role and the Power of the Swiss Judge in the Application of Penal Sanctions (French: Le Rôle et les pouvoirs du juge suisse dans l'application des sanctions pénales).
From 1972 to 1975, Marty worked at the Max Planck Institute for Foreign and International Criminal Law in Freiburg, Germany, responsible for the section on Swiss law.
In 1975, Marty was nominated state prosecutor of Ticino, in which post he was specially noted for his energetic activities fighting organized crime and drug abuse. For his achievements in the area of drug legislation, he received in 1987 an Award of Honor of the United States Department of Justice and a special award of honor by the International Narcotic Enforcement Officers Association. In 1989 he was elected a member of the cantonal executive in Ticino, where he was director of the finance department, and in 1992 additionally held the office of president, which rotates among the members. In 1995, upon being elected to the Swiss Council of States for Ticino, he resigned from his executive post and has since worked part-time as a legal and economic consultant.
In the Council of States he has been member of key commissions, including the Finance Commission and Economy and Taxes Commission, and took an active part in getting the new Swiss constitution through parliament.
In 1998 Marty was appointed as a member of the Parliamentary Assembly of the Council of Europe, where he became a member of its Monitoring Committee. He was later second vice-chairman of the Political Affairs Committee, with further positions in sub-committees.
In 2005, Marty was appointed to lead an investigation by the Council of Europe into alleged unlawful CIA prisons in Europe. Marty was planning to use satellite images and aviation logs, among many other sources of information, to find out whether the "rendition" of terror suspects for possible torture, or for secret detention, had taken place in any of the Council of Europe's 47 member states. These activities could be a violation of European human rights standards. In June 2006 Marty released his report on behalf of the Parliamentary Assembly, concluding that evidence showed that fourteen European states had assisted in the perpetration of such abuses.
Marty published the second part of this work on 8 June 2007, named Secret Detentions and Illegal Transfers of Detainees Involving Council of Europe Member States: Second Report.
On 14 December 2010, Marty published a report for adoption by the Council of Europe alleging inhuman treatment of people and killing of prisoners with the purpose of removal and illicit trafficking in human organs in Kosovo, involving Hashim Thaçi, the Kosovo prime minister and former Kosovo Liberation Army political leader.
Kosovo's leading politicians reacted strongly to Marty's report. Kosovo's acting president, Jakup Krasniqi, called the report "racist towards Albanians". Prime Minister Thaçi accused Marty of being "an opponent of Kosovo's independence" and called the report "politically motivated", "not based on facts", with the "goal to damage the newly-created state of Kosovo, Kosovo’s image, to question the election process, creation of institutions and Kosovo’s European future". As reported by several international, Serbian, Kosovan and Albanian news agencies, in an interview for Albanian TV Klan on 24 December 2010, Thaçi threatened to publish a list of Albanians who collaborated in providing information to Dick Marty for this report. On 25 January 2011, the Council of Europe endorsed the report and called for a full and serious investigation into its contents.
Marty acted as Special Rapporteur for the Assembly's Social, Health and Family Affairs Committee on the topic of euthanasia. His report and draft resolution, published in September 2003, called on Council of Europe members to collect empirical data on assisted dying, to promote debate and analysis of the evidence, and to consider whether legislation should be brought forward to exempt doctors from prosecution for assisting suicide under certain strict conditions. His stance proved controversial and the report was criticised by a number of organisations, such as the World Federation of Catholic Medical Associations and the Scottish Council on Human Bioethics. John Keown, a professor of Christian ethics at Georgetown University in Washington, DC, described it as "Mr Marty's muddle" and criticized him for "superficiality" and "selectivity."
The Committee subsequently adopted a formal Opinion prepared by the British member Kevin McNamara, which criticised several of Marty's findings and conclusions and sought to replace the call for governments to consider legislation to legalise assisted dying with a resolution to "report back to the Parliamentary Assembly for further consideration". McNamara's amendments were criticised in turn by organisations such as the World Federation of Right to Die Societies. Keown's criticism of Marty's report was criticised by Guy Widdershoven of Maastricht University.
Marty's report, as amended, was rejected by 138 votes to 26. Marty said he hoped the issue would come before the Assembly again in the future.
Besides his political work, since 1996 Marty has been president of Tourism Switzerland. In addition, he serves as president of the Swiss Scoutism Foundation.
In January 2014 Marty was appointed as head of the Cycling Independent Reform Commission by the Union Cycliste Internationale, with a remit to investigate doping in the sport during the 1990s and 2000s.