Short answer. Generally, no. Under the rule on ejectment answers, any affirmative or negative defense you do not plead in your answer is deemed waived, with only one exception: lack of jurisdiction over the subject matter, which can still be raised later because it is never waived.
What the law says
Affirmative and negative defenses not pleaded therein shall be deemed waived, except lack of jurisdiction over the subject matter.
Rule 70, Section 6 — Answer. Read the full provision →
The default rule: defenses not pleaded are waived
Section 6 states this plainly: affirmative and negative defenses not pleaded in the answer shall be deemed waived. That means the answer is not just one opportunity among several to raise your defenses — in an ejectment case, it is effectively the only opportunity. If a defense that was available to you at the time is left out of the answer, the rule treats it as given up for the rest of the case, not as something you can introduce later once the proceedings are underway.
The one defense that survives
The rule carves out a single exception: lack of jurisdiction over the subject matter. Because subject-matter jurisdiction goes to the court's basic authority to hear the type of case at all, it is not something a party can lose merely by failing to raise it in the answer, and it can still be raised later in the proceedings. Every other defense — whatever its nature — does not get this protection under Section 6, no matter how strong it might have been if timely pleaded.
Why the ten-day answer period matters so much
Section 6 gives the defendant ten days from service of summons to file the answer and serve a copy on the plaintiff. Because that same answer is where every waivable defense must be raised, the short deadline and the waiver rule work together: a defendant who is slow to prepare, or who treats the answer as a placeholder to be filled in later, risks losing defenses permanently before the case even gets underway on the merits.
Counterclaims and cross-claims follow the same logic
The same section applies an equivalent rule to cross-claims and compulsory counterclaims: if they are not asserted in the answer, they are considered barred. This is not limited to defenses against the plaintiff's allegations — claims the defendant might have wanted to bring against the plaintiff, or against a co-defendant, are subject to the same use-it-or-lose-it timing. Any answer to those counterclaims or cross-claims must then be filed within ten days from service of the answer that raised them.