Part I. General Rules
Rule 14. 
when answers are based on information obtained from other persons, the party may so state, and
a party need not sign answers to interrogatories about persons with knowledge of relevant facts, trial witnesses, and legal contentions.
Answers to interrogatories may be used only against the responding party. An answer to an interrogatory inquiring about matters described in Rule 194.2(b)(3) and (b)(4) that has been amended or supplemented is not admissible and may not be used for impeachment.
Interrogatories about specific legal or factual assertions such as, whether a party claims a breach of implied warranty, or when a party contends that limitations began to run are proper, but interrogatories that ask a party to state all legal and factual assertions are improper. As with requests for disclosure, interrogatories may be used to ascertain basic legal and factual claims and defenses but may not be used to force a party to marshal evidence. Use of the answers to such interrogatories is limited, just as the use of similar disclosures under Rule 194.6 is.
Rule 191s requirement that a partys attorney sign all discovery responses and objections applies to interrogatory responses and objections. In addition, the responding party must sign some interrogatory answers under oath, as specified by the rule. Answers in amended and supplemental responses must be signed by the party under oath only if the original answers were required to be signed under oath. The failure to sign or verify answers is only a formal defect that does not otherwise impair the answers unless the party refuses to sign or verify the answers after the defect is pointed out.
Notes and Comments: Comment to 1999 change: