Retrieval Artist

A Science Fiction series by Kristine Kathryn Rusch that can be somewhat neatly summed up by the description "Detective Drama In Space".

In The Future, humankind has settled the solar system and the stars, met other alien species and formed the Earth Sphere Alliance with many of them. As part of the treaties that the alliance is based on, humans living on alien worlds (and aliens on human worlds) are subject to alien law, with sentinces handed down by the Multicultural Tribunal. The problems arise when alien law doesn't line up with human ideas of justice, forcing humans to suffer punishments for what wouldn't otherwise be considred crimes: a human could unknowingly earn themselves the death penalty (or worse) for picking a pretty alien flower, for example. This disparity has created an underground industry: the Disappearance service. For a price, they will help those wanted for alien crimes become Unpersons, giving them a new name, identity and home, usually forever separating them from anyone they ever knew. The system works because the Alliance can't afford to hire trackers for every Disappeared case, and so most disappearances are successful. Sometimes, however, a Disappeared needs to be found for other reasons, without arousing the attention of the law: to collect an inheritance, to be given important news, to be told that the charges against them have been dropped. This is the realm of the Retrieval Artist.

Miles Flint was a detective in the Armstrong Police force, in Armstrong Base on the moon; before that, a traffic cop, and before that a husband, father and computer security engineer, until his infant daughter died at the hands of negligent daycare workers and his wife eventually left him in the fallout. As a newly promoted detective, Flint was partnered with the sour and cynical but very competent Noelle DeRicci. The case they work together brings him into contact with the world of the Disappeared and with Paloma, a veteran Retrieval Artist. Facing the decision To Be Lawful or Good, he chooses good, resigning from the force and applying to Paloma to mentor him in the Retrieval Artist profession, then sets up shop. Over the course of the following books, Flint and DeRicci, working separately but often on related cases, find themselves at odds with threats involving the livelihood of individuals, the safety of the lunar colony, and interstellar politics.

Works in the series are:
 * The Retrieval Artist - The original short story that spawned the series, chronologically set between the first two novels.
 * The Disappeared - Miles' first case as a detective brings him in contact with the world of the Disappeared and challenges him with the choice to uphold justice or uphold the law.
 * Extremes - A death on the course of the Moon Marathon being investigated by DeRicci turns out to be connected to a Disappeared Miles has been hired to find, and a few things emerge: a bioengineered virus that threatens all of Armstrong Dome, and the fact that not all those who Disappear are truly innocent.
 * Concequences - A woman pardoned of her crimes whom Miles retrieved ends up dead along with her family. DeRicci is forced to consider Miles as a suspect and Miles digs deep into an old, brutal human conflict, both to clear his name and his conscience of the death.
 * Buried Deep - The Disty, an alien species with a web of deep and strange taboos surrounding death, control Mars under a treaty with the Alliance. When a decades-old human skeleton is discovered at a construction site, the Disty start to panic. When the Martian detectives on the case suspect that the skeleton was a Disappeared, they hire Miles Flint. Further investigation leads to a shocking revelation that threatens the very fabric of Human-Disty relations.
 * Paloma - Miles' old mentor is murdered and he mounts his own investigation dig into her shadowy past to get to the bottom of it. De Ricci has been promoted out of the department in the meantime, and a new detective, Bartholomey Nyquist, heads up the investigation on the legal side.
 * Recovery Man
 * Duplicate Effort

Tropes

 * Arson Murder and Lifesaving: DeRicci finally starts getting this and respect from her superiors at the end of Extremes.
 * Asshole Victim: Frieda Tay in Extremes, the woman that became the skeleton in Burried Deep
 * Casual Interstellar Travel: Mostly HandWaved and has minimal plot impact - it's just assumed to be far enough in the future where it's possible. It's not quite as casual as crossing the galaxy in a day, but Earth to Mars in a day is doable, and an interstellar trip would compare to an ocean cruise.
 * Cool Starship: The Emiline, Flint's private space yacht named after his dead daughter. It's the one thing he lets himself indulge in spending his fortune on, so it's richly furnished inside and out, including state of the art defense and security, plus police ship features such as a brig and handcuff attachment points.
 * Defective Detective: Flint's weak spot is the loss of his daughter and it takes considerable effort for him to not let others exploit it. De Ricci gets in trouble all the time because she's too honest and unable to keep her mouth shut, running afoul of her supporters.
 * Disproportionate Retribution: the crimes and punishments of many of the Alliance's alien members.
 * Eagle Eye Detection: DeRicci's specialty.
 * Everything Is Online: and search-able by Flint. Off-world data requires jumping through some extra hoops however.
 * The Federation: The Earth Sphere Alliance. Unlike the Trope Namer, humans aren't necessarily the highest regarded species in it: there's no pretense that humanity has evolved beyond Humans Are Flawed.
 * A Fool for A Client: A variation with Retrieval Artists standing in for lawyers: an untrained person trying to track a Disappeared on their own risks exposing that person to trackers or other enemies. Miles takes up the search for Katherine Lehari up only after her mother reveals that the father, Judge Lehari, already tried tracking her himself - his experience is with trackers working for the Multicultural Tribunal, who don't care what they might expose the Disappeared to.
 * Hacker Cave: Flint's office resembles one when all his equipment is visible, but he does a lot of his work on public terminals under fake identities when he doesn't want it traced back to him.
 * Intrepid Reporter: Ki Knowles, an ambitious reporter for Inter-Dome Media Going for The Big Scoop, placed in the antagonist seat as she's the sort known for Twisting the Words and going after skeletons in closets.
 * I Work Alone: Standard procedure for Retrieval Artists, whose default setting is not to trust anyone, and must guard their sources, clients and information jealously. The saying "Three people may keep a secret if two of them are dead" applies. It's usually justified, but Miles finds he still needs connections once in a while, whether it's for business or for friendship.
 * Only Electric Sheep Are Cheap: The Moon has hydroponic agriculture but real food, especially imported from Earth (expecially meat) is a luxury.
 * Private Detective: Retrieval Artists are essentially this, and inherit many of the common tropes: the cynacisim, the code of honor, the slightly dingy office, the Damsel in Distress knocking at the door...
 * Remember That You Trust Me: DeRicci attempts this with Miles in Concequences when she knows that Miles is withholding information from her in an investigation. It doesn't work: Miles has to protect his integrity, and he tells DeRicci off rather coldly in the process. (By the next book they've patched things up enough that they're going out to dinner together).
 * Rich Idiot With No Day Job: Having become independently wealthy at the end of The Disappeared, Miles doesn't have to work, and indeed can and does turn down many cases if he thinks the client wants to hire him for the wrong reasons. He eschews most of the "idiot" traits through, making him more of a "Rich Loaner With No Day Job".
 * Starfish Aliens: Most of the alien culture in the series are bipedal...and there the physical similarities to humans end.
 * To Be Lawful or Good: Depends on which side you're on. Disappearance services are not expressly illegal but using them is breaking the law. Police, lawyers and judges look down their nose at Retrieval Artists because they don't operate within the law, Retrieval Artists don't trust the law and generally work for good.
 * Working the Same Case: After Flint leaves the force, his work still crosses paths with it several times, although working with Retrieval Artists is officialy frowned on by the law, and the Retrieval Aritst's ethics mean Miles can't directly share information about his cases or clients with the police or his friends on it.