For those who were speaking about hearsay, here's a clarification.
Please don't confuse hearsay with a party admission. Admission of something, under oath or not, is still an admission of something.
By way of example: If you were at your divorce hearing, and said to the Judge: "She can have the bank account because I stole $5 from my best-friend's wallet last week, so I have money", and then you were prosecuted for stealing the $5, that statement would be clearly admissible in the criminal prosecution against you for the $5 larceny from the wallet. Notwithstanding that you made the statement in an unrelated action (the divorce action).
Compared to hearsay which would be: "Bob told me that Joe admitted to him that he took $5" if it is being offered to prove the truth of that statement, eg., that Joe admitted he took the $5. However, if you were only offering that to show that Bob said those particular words, it is not hearsay (not the truth of the statement itself [the stealing of the $5] but merely that the words were uttered [Bob actually said that]).
Hope that makes sense. It's a bit convoluted. About as much as the Rule against Perpetuities.
Additionally, testimony in a deposition is in fact under oath, and subject to penalties of perjury. It can be used to prove (or disprove) something based upon the testimony. "I took the $5" by Joe under oath is sufficient for the person who had their $5 taken to sue Joe to get the money back". It could also be introduced to a judge/jury to show the fact or to "impeach" Joe (if Joe testifies he never took the $5).