The title of this episode, "30", is an old reporters' shorthand which means "end of story." (It is also the title of a 1959 Jack Webb movie [star, director] about a day in the life of a Los Angeles newspaper.) In practice, the 30 was always written with hyphens fore and aft, as follows: -30-. A possible origin has been attributed to the early days of telegraphy when XXX signified "end of message." Since XXX represents 30 in Roman numerals, it's possible that writers, telegraphers, and typesetters switched to the Arabic numerals of 30. Whatever its origin, the use was established around the time of the Civil War. Since it was originally intended as an instruction to typesetters, its appearance has declined since the advent of computerized typesetting.
The opening sequence where Josh runs through the streets to the police station ends with the line, "I want to report a murder... My own." That line comes right out of the movie "D.O.A. (1949)" starring Edmund O'Brien, whose character has been poisoned with iridium.
Defenestration is the act of throwing someone or something out of a window. It is an antiquated term that isn't used often in modern vocabulary.
Actor Lee Tergesen, who plays Josh Lemle in this episode, has previously appeared in an earlier episode playing a different character. He has also appeared in a number of other series in the L&O universe including: Law & Order (1990); Homicide: Life on the Street (1993) (in which he had a recurring role); Law & Order: Special Victims Unit (1999); and Law & Order: LA (2010). He also appeared in Prescription for Death (1990), which was the 1990 pilot episode for the original Law & Order series.