Per C.R.S. 14-2-111, a putative spouse is "any person who has cohabitated with another to whom he is not legally married in the good faith belief that he was married to that person..." So the two important elements are (1) cohabitation, and (2) a good faith belief of marriage.
Putative spouse cases are few and far between - they are rare enough that most family attorneys, including this firm, have likely not litigated a putative spouse case, and there is also very little guidance from the courts on what facts are sufficient to establish someone as a "putative spouse".
The putative spouse statute may be thought of as a "fallback" in case someone has a good faith belief in marriage, but cannot establish the existence of either a ceremonial or a common law marriage. However, a putative spouse should not be confused with the concept of palimony, where some states (not Colorado) confer financial benefits on a couple who end their relationship, even though the couple themselves knew they were never married.
Factors to Determine Putative Spouse
As indicated, there is very little precedent out there telling people when someone qualifies as a putative spouse. This necessarily means that the outcome of each case will be very fact-specific.
The few cases there are agree on one point, however - if the would-be putative spouse knows that the other party is still legally married to someone else, he/she cannot have a good faith to be a putative spouse. People v. McGuire, 751 P.2d 1011 (Colo. App. 1987). And that applies even if the couple underwent a "celestial" or some other spiritual ceremony - a person cannot have two spouses, so knowledge of another marriage negates a putative spouse claim. Combs vs. Tibbitts, 148 P.3d 430 (Colo. App. 2006).
However, if a would-be spouse who was unaware that the other spouse was still legally married has a putative spouse claim. In Williams v. Fireman's Fund Ins. Co., 670 P.2d 453 (Colo.App. 1983), the couple went through a formal wedding ceremony, lived together, and had a child. But there was a problem - the husband was still technically married, as a California court had previously entered an interlocutory judgment dissolving that prior marriage, but that had never been reduced to writing, as required. The court found that the wife was a putative spouse with all the rights and benefits of a spouse, as she was unaware of the illegality of her marriage.
So who has a potential putative spouse claim? Realistically, it's likely limited to someone who tried to marry, going through a marriage ceremony or meeting the common law marriage requirements and is seemingly married, but is unaware of the facts or legal barriers which would make the marriage void - such as a problem in the ceremony, or the fact that the other party were still married.
Here's a news article about a real-world example of what courts would likely treat as a putative marriage - a couple which went through a wedding ceremony back in 1964, but had apparently not complied with the marriage license requirement. Unbeknownst to them, their "marriage" of the past 5 decades was not legal.
Legal Rights of Putative Spouse
Per C.R.S. 14-2-111, a putative spouse has all of the rights of a legal spouse, including maintenance, property division, etc. However, if the other party actually has a legal spouse, then the putative spouse's rights do not supersede the legal spouse's rights. Instead, the Colorado family law court "shall apportion property, maintenance, and support rights among the claimants as appropriate in the circumstances and in the interests of justice."
Once a party learns that the marriage is not valid, he/she ceases to be a putative spouse, and does not acquire any further rights as a putative spouse from that time onwards. Note that this does not take away any putative spouse rights already acquired, however.
The Social Security Administration recognizes a Colorado putative spouse, and confers benefits on a claimant who can establish her/himself as a putative spouse. SSR 80-2. But see PR05705.007 - the federal government is not bound by a determination from a Colorado family law court that someone is a putative spouse, and can substitute its own judgment if it believes that the state court was wrong.
Wikipedia article on Putative Marriage.