Well, of course you would think that the program would determine child support - I bet 99% of lawyers would think the same thing. It's not naive in the slightest! (It's the Dissomaster program - or a newer one, X-spouse - they are pretty much identical). And you would be absolutely right in the vast majority of cases. But - yours is obviously not in the majority.
The dissomaster does not ALWAYS apply once a child is over 18, because the once the child is an adult, the court no longer has the jursisdiction to award custody or visitation - the timeshare would not apply to an adult (even a severely disabled one). And of course in most cases there would not BE any child support once a child has reached the age of 18.
However, it is not mandatory that the Dissomaster be used for a disabled adult (it is mandatory for children under 18). And yes, you are right, when the dissomaster IS used, the court mostly looks at the info that is on the Income and Expense Declaration and whatever numbers you put into the Dissomaster determines what number it spits out for guideline child support.
The judge has the discretion to either use the Dissomaster or, instead, to look at the actual expenses of the child. I have included the code section at the very bottom - it says that the judge uses the guideline (which means the Dissomaster), but that the court can depart from it, which essentially means that the use of the Dissomaster is not mandatory. I decided to check with some colleagues and most had never had this issue come up, but one, who is a certified specialist, said that he's had the issue 3 times in the last 4 years and not once did the judge use the Dissomaster. However, this was in Alameda county, not Santa Clara - and as I said, it's discretionary.
Please note that I have been making some assumptions about your case; I am assuming that your daughter is living with her mother (your ex). If this is not the case and your daughter is living in a care facility, the dissomaster would not be used.
I am also assuming (or maybe you actually stated this) that you do not know how much your daughter will be receiving. Finally, I am assuming, just based on my experience with "the system", that what she will receive is SSI, and will not be a lot of money.
So please correct me if any of those assumptions are wrong.
Okay - so let's go back to the Dissomaster. I now think I understand the confusion; the money that you pay in support is not considered income to the custodial parent. The money that goes into the slot for her income is only income that she receives from working - or another source that is not you. This is a hard and fast rule when using the dissomaster. So...if you want me to use the Dissomaster to do a support calculation for you, I'd be happy to - it would only take a minute. And there is a slot in there (you have to know how to find it, though) for just this situation; SSI. But because I can do this with my eyes closed, I know what happens when you put in the SSI; nothing. It has no effect on the number that the dissomaster spits out - because, of course, it's regarded as welfare and therefore just does not affect how much support you would pay.
If you'd like me to do a calculation, send me your gross income, the mother's gross income and the timeshare, if it applies (I'm assuming that it does not - that she is with her mother 100% of the time, but of course I could (gasp) be wrong).
Most likely the best way to approach this is to run the Dissomaster and find out what it spits out for child support and then look at your wife's Income and Expense Declaration and figure out what she says the expenses of the child are - then take the amount that your daugter will receive and deduct it from the expenses and compare that with what the Dissomaster dictates - see which is less and offer that amount as support to settle the case.
And - here is the law dealing with this issue (some of it does not apply, like the interstate stuff, but scroll down to the 2nd paragraph from the end bottom and there's a section that does talk about how support is calculated)
Adult Indigent Children
Both parents of a child have an equal responsibility to maintain, to the extent of their ability, a child of whatever age who is incapacitated from earning a living and without sufficient means.13 Children for whom support is authorized under Family Code Section 3910 are generally referred to as ''adult indigent'' children. Parents may not, by agreement, abrogate their statutory duty to support an adult indigent child or attempt to divest the court of jurisdiction to order support for an adult indigent child14 (see § 40.04).
This continuing duty of support runs contrary to the general rule that a parent's support obligation terminates when the child attains majority or is otherwise emancipated.15 It is primarily intended to protect the public from the financial burden of supporting an individual whose parents are able to provide the requisite support.16 It does not provide for a right of action by a provider of services against the parents of an adult child.17 Nor does it provide for any liability to a public agency for reimbursement of benefits provided to the indigent child.18
The language ''incapacitated from earning a living and without sufficient means'' comes from former Civil Code Section 242(d), which defined ''child'' under the former Uniform Civil Liability for Support Act as including such a son or daughter of whatever age. This language has been held to be synonymous with that of another former statute, Civil Code Section 206, which imposed a duty of support on a parent of ''any person in need who is unable to maintain himself by work.''19 This language requires the child to demonstrate an inability to be self supporting because of a mental or physical disability or proof of inability to find work because of factors beyond the child's control.20 Thus, a child's indigence alone does not give rise to a parent's obligation of support under Family Code Section 3910.21
Under this limitation, adult indigent children may include the developmentally disabled,22 the emotionally disabled,23 and the mentally ill.24 They do not include incarcerated adult children25 or adult children whose resources are otherwise insufficient to allow them to attend college.26
In the interstate enforcement area, one court of appeal held that the (now former) Uniform Reciprocal Enforcement of Support Act (URESA)27 required application of the law of the state in which the alleged obligor
was present,27.1 even if the obligee
resided in another state. Thus, it held that a California resident was required to support his adult indigent daughter residing in New York, which also had adopted URESA.27.2 For discussion of current interstate enforcement law under the Uniform Interstate Family Support Act (UIFSA), see Chapter 151.27.3
Support for an adult indigent child may be ordered in a proceeding for dissolution of marriage.27.4 The duty to support adult indigent children may also be enforced in an action under Family Code Section 4000 (see § 40.41). For a form of complaint to obtain support for an adult indigent child, see § 40.101.
In determining the amount of support a parent is required to pay for an adult indigent child under Family Code Section 3910, a judge must use the statewide uniform child support guideline set forth in Family Code Section 4050 et seq. (see § 41.05, et seq.). To the extent that the guideline embodies assumptions that are true of minor children, but not of adult disabled children, the guideline permits a trial court to adapt or depart from the basic child support formula in accordance with the ''special circumstances'' of the adult disabled child or the child's parents.27.5
Insurance that covers dependent children up to a limiting age must allow continuation of coverage beyond that age for seriously disabled children who meet certain criteria.27.6 A support order must require a parent who provides health insurance coverage for a supported child to seek continuation of coverage if the child meets these criteria and the continuation coverage is available at no cost or at a reasonable cost.27.7