A person is guilty of the offence of perjury if he has sworn as a witness or as an interpreter in a judicial proceeding, he lawfully makes a statement material in that proceeding which he knows to be false or does not believe to be true. this is how perjury is defined under English laws. In India the offence of perjury is described as GIVING FALSE EVIDENCE and has been mentioned under section 191 of IPC. The section describes it as "whoever, being legally bound by an oath or by na express provision of law to state the truth, or being bound by law to make a declaration on any subject, makes any statement which is false, and which he either knows or believes to be false or does not believe to be true, is said to give false evidence."
From the definition given in IPC the following elemrnts can be said to omprise the offence:-
1. a false statement
2. by a person bound by an oath, or;
3. by express provision of law
4. A declaration which he is bound by law to make on a subject
5. the statement or declaration made is false or which he knows to be false or not true.
The woeds bound by oath implies that the person is under legal obligation to state the truth. The main objective of administering the oath is to make a liable for giving false evidence. Therefore, when a person binds himself to oath in the court of law, he is bound to state the truth which in your case clearly did not happen. According to the facts stated by you, the persons concerned, intentionally stated the wrong facts even when they were under oath. This will amount to giving false evidence as the stated facts fulfills the the 3 main prerequisites of intentionally made flase statements, those being:-
(i) statement was false,
(ii) the persons knew that it was false,
(iii) the statement was made intentionally.
Now coming to the last part of your question, that is, the case being filrd the defendant. In the first paragraph we dealt wth the definition of the offence uner section 191 and it expressly starts with the expression "whoever", that means any person who makes a false a statement under oath can be made liable of the offence under section 191 whether it is complainant or defendant.
Now if we look at the heading of the chapter under which this offence is described, it reads as OF FALSE EVIDENCE AND OFFENCES AGAINST PUBLIC JUSTICE. Here, the term public justice becomes very important. It means that not every incorrect statement makes a person liable for prosecution. Prosecution for giving false evidence should be made only if it is in the expedient interest of justice. However, in Mishrilal v. State of Madhya Pradesh, the court stated that i witnesses are giving false evidence before before court and if it isproved satisfactorily the court should take srious action against them without aallowing them to go with certain expalanations or reasons for lying on oath. This decision was made because most of the witnesses coming to the court were giving false statements under oath. If stict actions will not be taken the evil of perjury will wreck and pollute the justice dispensation system.
I hope i answered your question. THANK YOU.