Before applying for an expired trademark, it is recommended to verify whether the trademark is still used by the entity that previously owned it. Not only can the owner revive the mark within six months after expiration, but even after this grace period, they can still be using it in commerce - either under a common law trademark or simply because they might not be aware that it has expired. Another reason for expiration might be not responding to an office action issued by the IPO in time, which the previous owner might be able to bounce back from.
As trademark examination is becoming ever more strict, all of the above should be taken into account before filing a trademark application for an expired trademark. Having an experienced trademark attorney look into the case would be highly recommended.