In the Harrisongs case, the court determined that George Harrison's My Sweet Lord subconsciously infringed the Chiffons’ 1963 hit He’s So Fine. Innocence is only significant when it comes to calculating monetary damages and attorney's fees. Bad-faith infringers are treated more harshly than innocent ones.
When Mark Twain was accused of subconsciously cribbing the dedication to the ironically titled The Innocents Abroad from a book of poems by Oliver Wendell Holmes, he quipped, "Adam was the only man who, when he said a good thing, knew that nobody had said it before him.” An argument can be made that "No Copyright Infringement Intended" trumpets the fact that the defendant knew they were infringing, or recklessly disregarded that possibility. If the infringement is willful, or your behavior reckless, a court can award up $150,000 per infringement together with attorney's fees.
As George Harrison learned, under copyright law, ignorance (or innocent intent) is not bliss. If you intend to use or reuse someone else’s copyrighted work, first educate yourself about fair use, the public domain, and what is - and isn't -- protected by copyright.
ResourcesFitzgerald Pub. Co., Inc. v. Baylor Pub. Co., Inc., 807 F. 2d 1110 - Court of Appeals, 2nd Circuit 1986
ABKCO Music, Inc. v. Harrisongs Music, Ltd., 722 F. 2d 988 - Court of Appeals, 2nd Circuit 1983