Mueller's office just filed notice of evidence it plans to present at trial about "prior acts" by Paul Manafort that he isn't facing charges for, but that prosecutors say is probative assets.documentcloud.org/documents/4516… 
Generally prosecutors can't introduce evidence of alleged bad acts that aren't charged at trial, but there are exceptions if it serves a purpose other than just attacking a defendant's character. It's known as 404(b) evidence, see: law.cornell.edu/rules/fre/rule…
The govt has to disclose 404(b) evidence in advance of trial, to give the defense notice so they can prepare. Here, Mueller's office says there are three categories of evidence about Manafort that they plan to introduce as 404(b) evidence assets.documentcloud.org/documents/4516…
Manafort could move to exclude 404(b) evidence. But Mueller's office also argues at least some of this evidence, such as about Manafort allegedly structuring payments to a law firm to avoid Ukrainian procurement limits, is "intrinsic" to the charges, so it's not even 404(b) ev
