Intellect • Trained Only
Expertise skills measure what your character knows about various things, whether you know anything about them or not. It’s fairly easy to measure what a hero knows by making the appropriate skill check or looking at the routine check value of (bonus +10).
However, players may know things their characters do not, either because of the player’s life experience or knowledge of the game and its rules (and source material). In this case the Gamemaster may prefer players limit themselves to only what Expertise skills their heroes have rather than what they may or may not know about a given situation. The GM may bend this rule by allowing a player to spend a victory point to have a character act upon something he or she would have no way of knowing, calling it a “hunch” or a “lucky guess” (a version of the inspiration rule). See Victory Points.
If there’s a question as to how to handle an issue of player versus character expertise in the game, consult your Gamemaster. Expertise is a broad skill encompassing knowledge and training in a variety of specialized fields, particularly professional disciplines and scholarship. Each is considered a separate skill and training in each is acquired separately, so a former police officer turned district attorney might have Expertise: Police Officer and Expertise: Law, each with their own ranks, for example.
If you are trained in an Expertise, you can practice and make a living at it. You know how to use the tools of that trade, perform the profession’s daily tasks, supervise untrained helpers, and handle common problems. For example, someone trained in Expertise: Sailor knows how to tie basic knots, tend and repair sails, and stand a deck watch at sea. The GM sets DCs for specific tasks using the guidelines provided in The Basics under Checks, keeping in mind that most job-related checks should be considered routine.
You can also make Expertise checks to see if your character knows the answer to a particular question related to the area of expertise, such as a scientist confronted with a technical issue, or a lawyer considering a legal question. The DC is 10 for easy questions, 15 for basic questions, and 20 or higher for difficult questions. You can usually answer questions as a routine check, and the GM may make a check for you in secret, so you won’t know whether or not your character’s skill is entirely up to the task.
Expertise covers all areas except those tasks specifically covered by other skills. So, for example, a police detective is going to be trained in Investigation (and probably Insight and Perception) in addition to Expertise: Police Officer, the same for an intrepid reporter with Expertise: Journalism. A scientist might be trained in Technology alongside Expertise: Science, a doctor needs training in Treatment along with Expertise: Physician, and a trial lawyer is going to want skill in Insight and Persuasion (and possibly Deception) along with the training in the law that comes with Expertise: Lawyer.
The ability modifier for Expertise is typically Intellect, but some areas of expertise may call for different abilities, perhaps depending on the task involved. For example, a technical expert might rely on Intellect to answer questions and handle day-to-day procedures, but need Dexterity to perform the actual functions of the job. Performance skills, such as acting or music, may rely on Presence. The GM sets the ability modifier as needed for the specific Expertise check.
Characters with expertise in a profession are also assumed to be licensed or certified to practice it, if necessary. Problems like licensing issues, professional rivalries, and so forth can be handled as complications.
The GM may allow some Expertise checks to be made untrained, especially for “unskilled” areas, measuring broad general knowledge and life experience, but even then an untrained Expertise check cannot be routine, and the character can only handle easy or basic tasks or questions (DC 10-15).
The following are examples of suitable areas of Expertise. This list is by no means exhaustive, the GM should feel free to add to or modify this list as needed to suit the game and the characters in it.
Art, Business, Carpentry, Cooking, Criminal, Current Events, Dance, History, Journalism, Law, Law Enforcement, Medicine, Military, Music, Magic, Philosophy, Politics, Popular Culture, Psychiatry, Science, Sociology, Streetwise, Theology
On occasion, the GM may decide that training in an Expertise skill provides some ability to deal with tasks covered by other, related, skills with a circumstance penalty to the skill check.
Example: Figuring out a particular clue involving a government conspiracy requires an investigation or expertise: Politics check. However, the GM allows a hero to substitute an Expertise: Law check with a –2 circumstance penalty, as the knowledge is related, but outside the character’s specific field. Expertise: Journalism might suffer a –5 penalty, but could still be useful (especially if the character works a legal or political beat as a reporter), while Expertise: Cooking is no help at all, and cannot be used for the check (unless the player comes up with a very clever explanation!)
D20Hero SRD Skills article- http://www.d20herosrd.com/4-skills