Van Deventer was a son of Christiaan Julius van Deventer and Anne Marie Busken Huet.
His uncle was the writer Conrad Busken Huet.
He married Elisabeth Maria Louise Maas; they had no children.
Van Deventer attended the H.B.S. in Deventer and studied law at Leiden University.
He achieved his doctorate in September 1879 on the thesis: "Zijn naar de grondwet onze koloniën delen van het rijk" ("are, according to the constitution, our colonies part of the Dutch empire").

On 20 August 1880 he was made available to the Governor-General of the Dutch East Indies by the Ministry of Colonies to be appointed as civil service official.
With his wife Van Deventer travelled in September 1880 to Batavia by steamboat Prins Hendrik; he was appointed court clerk at the Raad van Justitie (Council of Justice) at Amboina in December 1880.
As early as 1881 Van Deventer was already seen by the public as an authority in the case of the issue of the economic position of the Dutch East Indies in relation to motherland the Netherlands.
In lectures held during meetings of the "Indisch Genootschap" ("Indies Institute") his opinion on this matter was presented as very important.

In June 1882 Van Deventer was appointed court clerk at the "Landraden" (land boards) of Amboina, Saparua and Wahoo; he was also appointed auditeur militair (a legal position) at the court-martial in Amboina.
In March 1883 he was appointed member of the Council of Justice in Semarang and that same year he wrote a series of articles in the Soerabaijasch Handelsblad, under the title Gedichten van F.L. Hemkes (poetry by F.L. Hemkes; Frederik Leonardus Hemkes was a Dutch poet, who lived in South-Africa (1854–1887)).
Van Deventer wrote in February 1884 an article in "Het Indisch Weekblad voor het Recht" (The Dutch Indies Journal of Law), called De Indische Militairen en het Koninklijke Besluit van 13 Oktober 1882 nummer 26 (The military in the Dutch East Indies and the royal order of 13 October 1882), in which he discussed the trial of a Buginese soldier in front of a civil (police) court instead of a military one.
In April 1885 Van Deventer quit his job as a member of the Council of Justice in Semarang and was appointed lawyer and attorney at this Council of Justice.
In this period of his life Van Deventer was also active as a second lieutenant in the schutterij.
That same year, 1885, he quit his job at the Council of Justice and joined the legal practice of LLM B.R.W.A. baron Sloet van Hagensdorp and LLM M.H.C. van Oosterzee; he replaced mr.
Van Oosterzee, who would return to the Netherlands.
Van Deventer was a son of Christiaan Julius van Deventer and Anne Marie Busken Huet. His uncle was the writer Conrad Busken Huet. He married Elisabeth Maria Louise Maas; they had no children. Van Deventer attended the H.B.S. in Deventer and studied law at Leiden University. He achieved his doctorate in September 1879 on the thesis: "Zijn naar de grondwet onze koloniën delen van het rijk" ("are, according to the constitution, our colonies part of the Dutch empire").
On 20 August 1880 he was made available to the Governor-General of the Dutch East Indies by the Ministry of Colonies to be appointed as civil service official. With his wife Van Deventer travelled in September 1880 to Batavia by steamboat Prins Hendrik; he was appointed court clerk at the Raad van Justitie (Council of Justice) at Amboina in December 1880. As early as 1881 Van Deventer was already seen by the public as an authority in the case of the issue of the economic position of the Dutch East Indies in relation to motherland the Netherlands. In lectures held during meetings of the "Indisch Genootschap" ("Indies Institute") his opinion on this matter was presented as very important.
In June 1882 Van Deventer was appointed court clerk at the "Landraden" (land boards) of Amboina, Saparua and Wahoo; he was also appointed auditeur militair (a legal position) at the court-martial in Amboina. In March 1883 he was appointed member of the Council of Justice in Semarang and that same year he wrote a series of articles in the Soerabaijasch Handelsblad, under the title Gedichten van F.L. Hemkes (poetry by F.L. Hemkes; Frederik Leonardus Hemkes was a Dutch poet, who lived in South-Africa (1854–1887)). Van Deventer wrote in February 1884 an article in "Het Indisch Weekblad voor het Recht" (The Dutch Indies Journal of Law), called De Indische Militairen en het Koninklijke Besluit van 13 Oktober 1882 nummer 26 (The military in the Dutch East Indies and the royal order of 13 October 1882), in which he discussed the trial of a Buginese soldier in front of a civil (police) court instead of a military one. In April 1885 Van Deventer quit his job as a member of the Council of Justice in Semarang and was appointed lawyer and attorney at this Council of Justice. In this period of his life Van Deventer was also active as a second lieutenant in the schutterij. That same year, 1885, he quit his job at the Council of Justice and joined the legal practice of LLM B.R.W.A. baron Sloet van Hagensdorp and LLM M.H.C. van Oosterzee; he replaced mr. Van Oosterzee, who would return to the Netherlands.
Conrad Theodor van Deventer