Respondent failed to protect the interests of her client when she represented complainant, who is the opposing party of her client Leomarte Tamaray, in the same case. The responsibilities of a lawyer under Canon 17 were discussed in Penilla v. Alcid, Jr.:64 The legal profession dictates that it is not a mere duty, but an obligation, of a lawyer to accord the highest degree of fidelity, zeal and fervor in the protection of the client's interest. The most thorough groundwork and study must be undertaken in order to safeguard the interest of the client. The honor bestowed on his person to carry the title of a lawyer does not end upon taking the Lawyer's Oath and signing the Roll of Attorneys. Rather, such honor attaches to him for the entire duration of his practice of law and carries with it the consequent responsibility of not only satisfying the basic requirements but also going the extra mile in the protection of the interests of the client and the pursuit of justice[. ]65 Respondent is reminded of the duties and responsibilities of members of the legal profession, as discussed in Tenoso v. Echanez:66 Time and again, this Court emphasizes that the practice of law is imbued with public interest and that "a lawyer owes substantial duties not only to his client, but also to his brethren in the profession, to the courts, and to the nation, and takes part in one of the most important functions of the State-the administration of justice-as an officer of the court." Accordingly, "[l]awyers are bound to maintain not only a high standard of legal proficiency, but also of morality, honesty, integrity and fair dealing. "67 (Citations omitted) IV This court notes that respondent may have violated Canon 15, Rule 15.03 when she entered her appearance as counsel for complainant68 even though she was engaged as counsel by Leomarte Tamaray.69 Canon 15, Rule 15.03 of the Code of Professional Responsibility provides: CANON 15 - A lawyer shall observe candor, fairness and loyalty in all his dealings and transactions with his client. .... Rule 15.03 - A lawyer shall not represent conflicting interests except by written consent of all concerned given after a full disclosure of the facts. The rationale for Canon 15 was discussed in Samson v. Era:70 The rule prohibiting conflict of interest was fashioned to prevent situations wherein a lawyer would be representing a client whose interest is directly adverse to any of his present or former clients. In the same way, a lawyer may only be allowed to represent a client involving the same or a substantially related matter that is materially adverse to the former client only if the former client consents to it after consultation. The rule is grounded in the fiduciary obligation of loyalty. Throughout the course of a lawyer-client relationship, the lawyer learns all the facts connected with the client's case, including the weak and strong points of the case. Knowledge and information gathered in the course of the relationship must be treated as sacred and guarded with care. It behooves lawyers not only to keep inviolate the client's confidence, but also to avoid the appearance of treachery and double-dealing, for only then can litigants be encouraged to entrust their secrets to