This article quantifies and characterizes existing legal complaints for the sexual transmission of HIV in Spain, describes temporal trends and whether advance of scientific knowledge is reflected in charging decisions, judicial reasoning, and sentences. Sentences and writs dictated by Spanish penal and civil jurisdictions between 1981 and 2012 were obtained through legal databases systematic search. Sixteen sentences and 9 writs belonging to 19 cases were included; 17 judged by penal and two by civil jurisdictions. The first sentence was pronounced in 1996, 3 between 1999 and 2000, 4 between 2001 and 2005, and 18 between 2006 and 2012. In 10 (53%) cases there was effective HIV transmission, there was not in 6 (32%) and in 3 (15%) directionality could not be determined. Of the defendants, 15 (79%) were heterosexual males, 1 of which was an injecting drug user (IDU), 3 were men who have sex with men (MSM), and 1 was a heterosexual woman. In the 10 cases of HIV transmission, the mechanism was heterosexual sex and index cases were males in nine occasions. Disclosure of HIV status, use of condoms and its frequency, and its possible breaks were mentioned in only some sentences/judicial decisions and fewer mentioned the use of antiretroviral treatment. Very few cases referred to plasma viral load (VL), and there are incorrect statements regarding HIV transmissibility. Only one 2012 sentence mentioned VL levels, adherence to ART, CD4 lymphocyte levels, concomitant sexually transmitted infections, and references to pertinent literature. The number of judicial decisions in Spain is increasing and the profile of the plaintiffs, largely heterosexual women, does not reflect the groups most affected by the HIV epidemic, largely IDU and MSM. Most judgments and writs do not reflect HIV scientific and technical advances. It is of utmost importance that these complex processes incorporate the most up-to-date knowledge on the subject.