A method of stabilizing a biological sample for analysis, comprising the steps of: a. obtaining in a sample collection container a biological sample from a subject selected from a victim of a crime, a suspect of a crime, a subject undergoing detection and/or monitoring of a cancerous condition, a subject undergoing detection and/or monitoring of a neurogenerative condition, a subject undergoing detection and/or monitoring of a psychiatric condition, or a subject who is not pregnant, wherein the biological sample includes at least one circulating cell-free first nucleic acid from the subject; b. contacting the biological sample while within the sample collection container with a protective agent composition that includes - at least one preservative agent selected from diazolidinyl urea, imidazolidinyl urea, dimethoylol-5,5-dimethylhydantoin, dimethylol urea, 2-bromo-2.-nitropropane-1,3-diol, oxazolidines, sodium hydroxymethyl glycinate, 5-hydroxymethoxymethyl-1-laza-3,7-dioxabicyclo-[3.3.0]octane, 5-hydroxymethyl-1-1aza-3,7dioxabicyclo[3.3.0]octane, 5-hydroxypoly-[methyleneoxy]methyl-1-1aza-3,7dioxabicyclo [3.3.0] octane, quaternary adamantine or any combination thereof, - an optional anticoagulant, and - a quenching agent to form a mixture that includes the protective agent composition and the sample, wherein the contacting step includes employing as the quenching agent an ingredient selected from glycine, lysine, ethylene diamine, arginine, urea, adenine, guanine, cytosine, thymine, spermidine, or any combination thereof; c. quenching any free formaldehyde that may be present with the quenching agent from the protective agent composition so that the free formaldehyde reacts to form a reaction product that is inert to the first nucleic acid of the biological sample, the resulting mixture is devoid of any aldehyde, and nucleic acids within the sample are suitable for polymerase chain reaction and DNA sequencing, and DNA and are substantially devoid of aldehyde induced (i) nucleic acid (e.g., DNA) to protein cross-linking, (ii) nucleic acid (e.g., DNA) to nucleic acid (e.g., DNA) intra-molecular and/or inter-molecular cross-links; or both (i) and (ii), to thereby form a sample that is amplifiable by polymerase chain reaction, and DNA sequencing; wherein the biological sample comes from or is in the initial form of one or more biological matter selected from urine, saliva, feces, synovial fluid, cerebrospinal fluid, or peritoneal fluid. a. obtaining in a sample collection container a biological sample from a subject selected from a victim of a crime, a suspect of a crime, a subject undergoing detection and/or monitoring of a cancerous condition, a subject undergoing detection and/or monitoring of a neurogenerative condition, a subject undergoing detection and/or monitoring of a psychiatric condition, or a subject who is not pregnant, wherein the biological sample includes at least one circulating cell-free first nucleic acid from the subject; b. contacting the biological sample while within the sample collection container with a protective agent composition that includes - at least one preservative agent selected from diazolidinyl urea, imidazolidinyl urea, dimethoylol-5,5-dimethylhydantoin, dimethylol urea, 2-bromo-2.-nitropropane-1,3-diol, oxazolidines, sodium hydroxymethyl glycinate, 5-hydroxymethoxymethyl-1-laza-3,7-dioxabicyclo-[3.3.0]octane, 5-hydroxymethyl-1-1aza-3,7dioxabicyclo[3.3.0]octane, 5-hydroxypoly-[methyleneoxy]methyl-1-1aza-3,7dioxabicyclo [3.3.0] octane, quaternary adamantine or any combination thereof, - an optional anticoagulant, and - a quenching agent to form a mixture that includes the protective agent composition and the sample, wherein the contacting step includes employing as the quenching agent an ingredient selected from glycine, lysine, ethylene diamine, arginine, urea, adenine, guanine, cytosine, thymine, spermidine, or any combination thereof; - at least one preservative agent selected from diazolidinyl urea, imidazolidinyl urea, dimethoylol-5,5-dimethylhydantoin, dimethylol urea, 2-bromo-2.-nitropropane-1,3-diol, oxazolidines, sodium hydroxymethyl glycinate, 5-hydroxymethoxymethyl-1-laza-3,7-dioxabicyclo-[3.3.0]octane, 5-hydroxymethyl-1-1aza-3,7dioxabicyclo[3.3.0]octane, 5-hydroxypoly-[methyleneoxy]methyl-1-1aza-3,7dioxabicyclo [3.3.0] octane, quaternary adamantine or any combination thereof, - an optional anticoagulant, and - a quenching agent to form a mixture that includes the protective agent composition and the sample, wherein the contacting step includes employing as the quenching agent an ingredient selected from glycine, lysine, ethylene diamine, arginine, urea, adenine, guanine, cytosine, thymine, spermidine, or any combination thereof; c. quenching any free formaldehyde that may be present with the quenching agent from the protective agent composition so that the free formaldehyde reacts to form a reaction product that is inert to the first nucleic acid of the biological sample, the resulting mixture is devoid of any aldehyde, and nucleic acids within the sample are suitable for polymerase chain reaction and DNA sequencing, and DNA and are substantially devoid of aldehyde induced (i) nucleic acid (e.g., DNA) to protein cross-linking, (ii) nucleic acid (e.g., DNA) to nucleic acid (e.g., DNA) intra-molecular and/or inter-molecular cross-links; or both (i) and (ii), to thereby form a sample that is amplifiable by polymerase chain reaction, and DNA sequencing;