Challenges for cause may be taken on one or more of the following grounds:
(1) a want of any of the qualifications prescribed by this code to render a person competent as a juror;
(2) being the spouse of or related to a party by consanguinity or affinity within the sixth degree;
(3) standing in the relation of guardian and ward, debtor and creditor, employer and employee, or principal and agent to either party or being a partner in business with either party or surety on any bond or obligation for either party. However, a challenge for cause may not be taken because of debtor and creditor relation when the same arises solely:
(a) by reason of current bills of gas, water, electricity, or telephone; or
(b) because a prospective juror is a depositor of funds with a bank, savings and loan institution, credit union, or similar financial institution.
(4) having served as a juror or been a witness on a previous trial between the same parties for the same cause of action;
(5) interest on the part of the juror in the event of the action or in the main question involved in the action, except the juror's interest as a member or citizen of a municipal corporation;
(6) having an unqualified opinion or belief as to the merits of the action;
(7) the existence of a state of mind in the juror evincing enmity against or bias in favor of either party.