Obtaining compromising photos depicting someone's infidelity and then threatening to reveal them to the person's spouse unless he pays up is an example of "black mail" or extortion.
Blackmail as such is prohibited by California Penal Code 518. Specifically, Penal Code 518 makes it illegal to use force or threats to compel someone to give you money or other property. This includes threats to accuse the targeted person of a crime, to reveal a secret about him or his family, or to expose him to embarrassment or disgrace.
A person commits blackmail under California extortion law even if he had every right to carry out the threat. For instance, suppose Sally works at Starbucks and notices a coworker stealing money from the cash register. She threatens to report this unless the coworker gives her a cut.
Sally certainly has a right to report her coworker's misconduct...and possibly even a moral and job duty to do so. But it's a crime to take advantage of the situation by trying to extort money from the culprit. Blackmail subjects her to up to four years of California state prison.
That said, very few California extortion cases are totally cut and dry. People often get wrongfully accused and the facts and evidence are many times quite ambiguous. If you've been accused of blackmail or extortion, seek the help of a criminal defense attorney as quickly as possible.
California Penal Code 518 - 527
California Penal Code 518. Extortion is the obtaining of property from another, with his
consent, or the obtaining of an official act of a public officer, induced by a wrongful use of force or fear, or under color of official right.
California Penal Code 519. Fear, such as will constitute extortion, may be induced by a
threat, either: 1. To do an unlawful injury to the person or property of the
individual threatened or of a third person; or, 2. To accuse the individual threatened, or any relative of his, or member of his family, of any crime; or, 3. To expose, or to impute to him or them any deformity, disgrace or crime; or, 4. To expose any secret affecting him or them.
California Penal Code 520. Every person who extorts any money or other property from
another, under circumstances not amounting to robbery or carjacking,
by means of force, or any threat, such as is mentioned in Section
519, shall be punished by imprisonment in the state prison for two,
three or four years.
California Penal Code 521. Every person who commits any extortion under color of official
right, in cases for which a different punishment is not prescribed in this Code, is guilty of a misdemeanor.
California Penal Code 522. Every person who, by any extortionate means, obtains from
another his signature to any paper or instrument, whereby, if such signature were freely given, any property would be transferred, or any debt, demand, charge, or right of action created, is punishable in the same manner as if the actual delivery of such debt, demand, charge, or right of action were obtained.
California Penal Code 523. Every person who, with intent to extort any money or other property from another, sends or delivers to any person any letter or other writing, whether subscribed or not, expressing or implying, or adapted to imply, any threat such as is specified in Section 519, is punishable in the same manner as if such money or property were actually obtained by means of such threat.
524. Every person who attempts, by means of any threat, such as is specified in Section 519 of this code, to extort money or other property from another is punishable by imprisonment in the county jail not longer than one year or in the state prison or by fine not exceeding ten thousand dollars ($10,000), or by both such fine andimprisonment.
525. Upon conviction of a felony violation under this chapter, the fact that the victim was an elder or dependent adult, as defined in Section 368, shall be considered a circumstance in aggravation when imposing a term under subdivision (b) of Section 1170.
526. Any person, who, with intent to obtain from another person any money, article of personal property or other thing of value, delivers or causes to be delivered to the other person any paper, document or written, typed or printed form purporting to be an order or other process of a court, or designed or calculated by its writing, typing or printing, or the arrangement thereof, to cause or lead the other person to believe it to be an order or other process of a court, when in fact such paper, document or written, typed or printed form is not an order or process of a court, is guilty of a misdemeanor, and each separate delivery of any paper, document or written, typed or printed form shall constitute a separate offense.
527. Any person who shall sell or offer for sale, print, publish, or distribute any paper, document or written, typed or printed form, designed or calculated by its writing, typing or printing, or the arrangement thereof, to cause or lead any person to believe it to be, or that it will be used as an order or other process of a court when in fact such paper, document or written, typed or printed form is not to be used as the order or process of a court, is guilty of a misdemeanor, and each separate publication, printing, distribution, sale or offer to sell any such paper, document or written, typed or printed form shall constitute a separate offense, and upon conviction thereof in addition to any other sentence imposed the court may order that all such papers or documents or written, typed or printed forms in the possession or under the control of the person found guilty of such misdemeanor shall be delivered to such court or the clerk thereof for destruction.