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Schreiber was born in Berlin to Paul Schreiber (a postal inspector) and his wife Gertrud Kettlitz. After completing gymnasium in Berlin, he studied medicine at the universities of Berlin, Tübingen, and Greifswald.
In 1914, he enlisted voluntarily for military service and served with the 42nd Infantry Regiment in France. He was injured at the First Battle of the Marne. After his recovery, he continued with his studies and served as a temporary doctor on the Western Front until the end of the war in 1918.
In 1933, he joined the Nazi Party.
In October 1942, Schreiber attended the conference, where the results of human experiments at Dachau were presented. In May 1943, he headed the third session of the advisory specialists of the Armed Forces. This led to a confrontation because of the experiments with typhus on concentration camp prisoners. In applying the Ipsenschen murine typhus vaccine Dr Rose was in 1943 commissioned to inquire with the Hygiene Institute of the Waffen-SS, whether in the Buchenwald concentration camp one could one test the vaccine on prisoners. In September 1943, Schreiber accepted the position of the commander of the Training Division C of the Military Medical Academy. In 1944, Dr Schreiber conferred with Dr. Karl Brandt, the attorney for health care, scientific advisory board.
On 26 August 1946 Schreiber gave evidence at the Nuremberg Trials in support of the Soviet Chief Prosecutor, Roman Rudenko. A recording of his testimony at the trial can be found at the online archive of the Imperial War Museum. The transcript link is here 
After presenting himself to the Allied military authorities in West Berlin, who interrogated him, Schreiber was hired to work with the Counter Intelligence Corps. In her book Secret Agenda, Linda Hunt reveals that Schreiber was employed at Camp King, a large POW interrogation center in Oberursel, Germany.
He arrived in New York on Sep 17, 1951 with his wife (Olga Conrad Schreiber) and son (Paul-Gerhard Schreiber) and mother in-law (Marie Conrad) on the USNS General Maurice Rose, (T-Ap216). The manifest of the ship does not list travel documents for them, but declares them to be "Paper Clips".
Schreiber was subsequently taken to the United States as part of Operation Paperclip. On 7 October 1951 the New York Times reported that he was working at the Air Force School of Medicine at Randolph Air Force Base in Texas.
When journalist Drew Pearson publicized Schreiber's Nuremberg evidence in 1952, which showed he had assigned doctors to experiment on concentration camp prisoners and had made funds available for such experimentation, the negative publicity led the Joint Intelligence Objectives Agency to arrange "a visa and a job for Schreiber in Argentina, where his daughter Elisabeth was living." On 22 May 1952 he was flown to Buenos Aires.
In Argentina, he worked at an epidemiological laboratory.
- fr:Walter Schreiber