Detectives were unable to locate any bloodstains or fingerprints at the scene of the crime. No plasma or bodily fluids left behind might have meant the child wasn't injured and a lack of fingerprints pointed to an abductor who was careful enough to conceal their identity.
Authorities continued to dig deeper into their investigation and when questioning the Lindbergh's household employees and staff. The couple banned together with investigators in an effort to unmask anyone associated with the crime.
Multiple attempts to communicate with the kidnapper(s) included widespread appeals to open negotiations with the perpetrator(s) in the press. Police and legal authorities were also cooperating with known criminals and mafia characters in hopes of connecting a suspect to the crime.
Six days after the abduction, there was a second ransom note received on March 6, 1932, postmarked in Brooklyn, New York. This time the demand was increased to $70,000. Attention to the case was massive with a police conference called by the governor of New Jersey attended by prosecutors and government officials. Lindbergh's attorney Henry Breckenridge employed private investigators to pry further into the case.
A third ransom demand was delivered to attorney Breckenridge's office just two days later on March 8th requesting a mention in the press. A fourth note was received by a local physician named Dr. Condon indicating he could be a possible go-between with an exchange of the ransom with the kidnapper. The next day, a fourth ransom note was received by the good doctor.