If they are found guilty of murder and kidnapping, and are given LWOP, then it just a waste of taxpayer money to have another trial for the fraud charges. They are already in jail for their rest of their lives. However, if they are found not guilty or somehow get a small sentence, then they can get them on something else (see: OJ). They are digging into the background, to find things completely unrelated to Heather's case, for a reason.
Yes, but you say "piling on the charges" in case they get acquitted like they're just bringing up charges for the heck of it. Regardless if they will spend life in prison w/o parole, they still need to have their backgrounds checked into, and the charges brought against them for what they did commit. Those charges could affect the trial, probably not directly but that's irrelevant. Doesn't mean they are immune to having the charges brought upon them because they could be (most likely!) will be spending life in prison.
Just for a little preview of what they're facing in addition to all their other charges...
OBTAINING SIGNATURE OR PROPERTY BY FALSE PRETENSE
Misdemeanor, Class E or F Felony
Code §16-13-240
CDR Codes 3469, 3470, 3471
Elements Of The Offense:
1.That the accused did obtain the signature of a person to a written instrument or did obtain property by false representation of a material fact, and
2.That the accused knew the representation to be false, and
3.That the representation was of a present or past fact, and
4.That the person from whom the goods were obtained relied upon the representation to be true, and
5.That the accused did intend to cheat or defraud the person from whom the goods were obtained.
Penalty: If the value of the property is $10,000 or more; fine of not more than $500 dollars and imprisonment for not more than 10 years.